Random reboots usually mean a hardware problem, a driver conflict, or overheating — not a software virus
When your computer restarts without warning, it is almost always protecting itself from damage. Windows and Mac systems are designed to shut down and reboot if they detect a serious problem — a failing hard drive, a power supply that cannot keep up, a graphics card driver that crashes, or temperatures climbing too high. The reboot happens before the system can fail completely or corrupt your files.
The frustrating part is that your computer does not always tell you what went wrong. You see a black screen, a flash of text you cannot read, and then the startup screen. To find the real cause, you need to check the system logs — the record of what your computer was doing when it decided to restart.
Key Takeaways
- Check the Windows Event Viewer or Mac Console to see what error message your computer logged at the moment of the reboot.
- Overheating is the most common cause of random reboots; clean dust from your fans and make sure air vents are not blocked.
- Update your graphics card driver and chipset driver first, because outdated drivers cause crashes that trigger automatic reboots.
- If reboots happen during specific programs or games, the problem is usually that program's incompatibility with your hardware or Windows version.
- If the reboot happens with no warning and no error message, suspect a failing hard drive or power supply — both need professional diagnosis.
How to read your computer's error log
Your computer records every crash and restart in a system log. On Windows, this is called the Event Viewer. On Mac, it is the Console app. Both are built in and free to open.
On Windows: Press the Windows key and type "Event Viewer" and open it. On the left side, click "Windows Logs," then click "System." Look for entries marked "Critical" or "Error" that happened at the exact time your computer rebooted. The description will often name the driver or component that failed — for example, "nvlddmkm.sys" (a graphics driver) or "disk" (a hard drive problem).
On Mac: Open Spotlight (Command + Space), type "Console," and open the Console app. Click "System Log Queries" on the left, then "Last Hour" or "Last 24 Hours." Look for lines that say "kernel panic" or "reboot" with a timestamp. The lines above it usually explain what triggered it.
Write down the exact error message or driver name you find. This is the single most useful piece of information you can have when troubleshooting.
Dust and overheating as the most common culprit
Computers generate heat, and they cool themselves by pulling air through fans and vents. When dust builds up on the fans or blocks the vents, the computer cannot cool itself. When the temperature reaches a critical threshold — usually around 90 to 100 degrees Celsius depending on your processor — the system reboots to protect the CPU from permanent damage.
Overheating reboots often happen during demanding tasks: gaming, video editing, or running multiple programs at once. You might notice the fan running very loudly just before the reboot, or feel hot air coming from the vents.
To check and clean: Shut down your computer completely and unplug it. Open the case (if you are comfortable doing so — consult your computer's manual for how). Use a can of compressed air to blow dust out of the fans and heatsinks. Pay special attention to the CPU cooler and any large fans. Do not touch the components themselves. Close the case, plug in, and restart.
If you are not comfortable opening the case, a computer repair shop can do this cleaning for $50 to $100. It is worth the cost if overheating is the cause, because a reboot-from-overheating computer can suffer permanent CPU damage if it keeps happening.
Outdated graphics and chipset drivers
Your graphics card and chipset have their own software, called drivers. These drivers tell Windows how to talk to the hardware. When a driver is outdated or corrupted, it can crash, and a crash in the graphics driver or chipset driver triggers an automatic reboot.
Graphics driver crashes often happen during gaming or when you are using multiple monitors. Chipset driver crashes can happen anytime, sometimes with no obvious trigger.
To update on Windows: Right-click the Start button and open Device Manager. Expand "Display adapters" and right-click your graphics card (usually NVIDIA, AMD, or Intel). Click "Update driver" and choose "Search automatically for updated driver software." Windows will read and install the latest version from the manufacturer. Restart when prompted.
For your chipset driver, go to your computer manufacturer's support website (Dell, HP, Lenovo, etc.), find your exact model number, and read the chipset driver from there. Install it and restart.
On Mac: Graphics drivers are built into macOS and update automatically when you run Software Update. Open System Settings, click "General," then "Software Update," and install any available updates.
Reboots during a specific program or game
If your computer reboots only when you run one particular program, the problem is usually that program's incompatibility with your hardware or your version of Windows.
Check the program's system requirements and compare them to your computer's specs. If your graphics card is older than the program expects, or if you are running an older version of Windows, the program may crash and trigger a reboot. Some older games, for example, were written for Windows 7 and do not work properly on Windows 10 or 11.
Try running the program in compatibility mode. Right-click the program's shortcut or .exe file, select "Properties," click the "Compatibility" tab, and check "Run this program in compatibility mode for:" and choose an older Windows version. Click "explore" and "OK," then try running the program again.
If that does not work, check the program's support website or forums to see if other users have reported the same reboot. Often there is a patch or a workaround posted there.
Hard drive failure and power supply problems
If your computer reboots with no error message, no warning, and no pattern — just suddenly goes black and restarts — suspect either a failing hard drive or a power supply that is failing.
A failing hard drive will sometimes log errors in the Event Viewer mentioning "disk," "I/O," or specific sector numbers. A failing power supply usually shows no error at all; the computer just loses power and reboots. You might notice the reboot happens more often when you are doing something demanding (gaming, video encoding) because that is when the power supply is under the most stress.
Both of these problems require professional diagnosis. A technician can run a hard drive test (using tools like CrystalDiskInfo on Windows or Disk Utility on Mac) or test the power supply with a multimeter. Do not ignore these reboots, because a failing hard drive can lose your data, and a failing power supply can damage other components.
Windows Update and BIOS updates
Sometimes a reboot is not random at all — it is Windows installing an update in the background. Windows 10 and 11 can restart without asking you first if you have not restarted in a while and an update is waiting.
Check Windows Update to see if updates are pending. Open Settings, click "System," then "About," and look for "Windows Update." If updates are waiting, click "Restart now" to install them on your schedule instead of having Windows choose the time.
Similarly, if your computer manufacturer released a BIOS update (the firmware that runs before Windows starts), installing it can cause a reboot. Check your computer manufacturer's support website to see if a BIOS update is available and when it was released. If it was released around the time your reboots started, that may be the cause.
When to call a professional
If you have checked the Event Viewer or Console and found an error message mentioning "disk," "hard drive," "power," or "PSU," or if the error message is a long string of numbers with no clear meaning, take your computer to a repair shop. These are signs of hardware failure that need professional testing.
If the reboots continue after you have cleaned the dust, updated your drivers, and checked for Windows updates, a technician can run diagnostic tests on your hard drive, power supply, and RAM to find the real cause. Most shops charge $50 to $100 for a diagnostic.
Frequently Asked Questions
Can a virus cause random reboots?
Viruses can cause reboots, but they are not the most common cause. A virus would usually show other signs first: slow performance, unexpected programs running, or pop-ups. If you suspect a virus, run a full scan with Windows Defender (built into Windows) or a third-party antivirus like Malwarebytes. If the reboots continue after a clean scan, the cause is almost certainly hardware or drivers, not malware.
Why does my computer reboot during startup?
Reboots during startup usually mean a corrupted Windows file, a failing hard drive, or a hardware incompatibility. Try restarting in Safe Mode (hold Shift while clicking Restart, then choose Troubleshoot > Advanced Options > Startup Settings). If Safe Mode works without rebooting, the problem is likely a driver or program that loads at startup. If Safe Mode also reboots, the problem is likely hardware or Windows corruption, and you should take it to a technician.
What does "automatic restart on system failure" mean?
This is a Windows setting that tells your computer to reboot automatically when it encounters a critical error, instead of showing you a blue screen and stopping. It is turned on by default. You can turn it off to see the actual error message: right-click "This PC" or "My Computer," click Properties, click "Advanced system settings," and under "Startup and Recovery," uncheck "Automatically restart." The next time an error happens, you will see the full message instead of a reboot.
Can RAM problems cause random reboots?
Yes. Faulty RAM (memory) can cause random reboots with no error message. If you suspect RAM, you can run the Windows Memory Diagnostic tool: press the Windows key, type "Memory Diagnostic," and open it. Choose to restart and run the test now. It will run automatically and report any errors. If errors are found, one of your RAM sticks is failing and needs to be replaced.
Should I disable automatic restart to see the error message?
Yes, if you want to see what error your computer is trying to tell you. Disable automatic restart (see the answer above), and the next time a critical error happens, your computer will show you a blue screen with an error code and message. Write down the exact message and search for it online, or take a photo and show it to a technician. This one piece of information often points directly to the cause.