What causes unexpected restarts

Your computer is restarting on its own because of one of a few common culprits: a Windows Update that finished installing and is forcing a restart, a hardware problem like overheating or a failing power supply, a driver that crashed, malware, or a software conflict. The restart happens because Windows detects a problem serious enough that it cannot continue running safely, so it shuts down and starts fresh.

The most common reason is Windows Update. If you see a notification saying "Your PC will restart in 15 minutes" or you notice restarts happening at the same time each day, Windows has finished an update and is enforcing the restart. This is by design—Microsoft does not let you postpone indefinitely. The second most common reason is overheating: if your computer is in a hot room, blocked by dust, or running heavy programs like video games or rendering software, the CPU or GPU temperature climbs until Windows shuts down to protect the hardware.

Less common but serious causes include a failing hard drive, a power supply that cannot deliver steady voltage, corrupted system files, or malware. If the restarts started after you installed new software or a driver, that software is often the culprit.

Key Takeaways

  • Windows Update is the most common cause; check Settings > Update & Security to see if an update is pending or recently installed.
  • Overheating forces restarts as a safety measure; clean dust from vents and fans, and make sure the computer has airflow around it.
  • Restart in Safe Mode to see if the problem stops—if it does, a driver or third-party software is causing it; if it continues, the problem is Windows itself or hardware.
  • Check the Event Viewer log (eventvwr.msc) to see what Windows recorded about each restart, which narrows down the cause.
  • If restarts continue after ruling out updates and overheating, back up your files and consider a clean Windows reinstall or a hardware diagnostic.

Check for pending Windows Updates

Open Settings by pressing Windows key + I, then go to Update & Security > Windows Update. Click "Check for updates" and let it scan. If an update is waiting to install, you will see it listed. If an update has already installed and is waiting for a restart, you will see a button that says "Restart now" or a countdown timer.

If you see a restart countdown, you have two options: restart now to get it over with, or click "Reschedule" to push it back a few hours. Windows will not let you postpone forever—after a certain number of days, it will force the restart during a time you are not using the computer. The restart is necessary because updates often patch security holes or fix bugs that affect stability.

After the restart completes, check Settings > Update & Security > Windows Update again and confirm it says "You are up to date." If restarts continue after this, move to the next step.

Clean dust and check for overheating

Shut down your computer completely and unplug it. Open the case or remove the side panel if you have a desktop, or flip the laptop over if you have a laptop. Look for dust buildup on the fans, heatsinks, and air vents. Dust blocks airflow and traps heat inside.

Use a can of compressed air to blow dust out of the vents and away from the fans. Hold the can upright and use short bursts. For a laptop, blow air out through the vents on the sides and bottom. Do not let the fans spin freely while you are blowing air—hold them gently in place so the force does not damage the bearings.

After cleaning, plug the computer back in and turn it on. Place it somewhere with good airflow: not in a closed cabinet, not on a bed or pillow, and not in direct sunlight. If you have a laptop, use a laptop stand or a hard, flat surface so air can flow underneath. read a free temperature monitor like HWInfo or Core Temp, run it while you use the computer normally, and watch the CPU and GPU temperatures. If they stay below 80°C (176°F) during normal use, overheating is not the problem. If they climb above 85°C, cleaning did not solve it and you may need a new fan or thermal paste.

Restart in Safe Mode to isolate the cause

Safe Mode loads Windows with only the drivers and services it absolutely needs to run. If your computer stops restarting in Safe Mode, a third-party driver or program is causing the problem. If it keeps restarting even in Safe Mode, the problem is Windows itself or hardware.

To enter Safe Mode, restart your computer and when ready press F8 repeatedly as it boots (on some computers it is F5 or Del—if F8 does not work, restart and try the others). You should see a menu with boot options. Select "Safe Mode" or "Safe Mode with Networking." The screen will look different and load more slowly than normal—that is correct.

Use the computer in Safe Mode for 10 to 15 minutes and do the things you normally do. If no restart happens, restart normally and go to the next step. If a restart happens in Safe Mode too, the problem is likely Windows corruption or hardware failure, and you should move to checking the Event Viewer or consider a clean Windows reinstall.

Check the Event Viewer log

The Event Viewer records every time Windows restarts and often logs the reason. Press Windows key + R, type eventvwr.msc, and press Enter. On the left side, click "Windows Logs," then click "System." You will see a long list of events.

Look for entries labeled "Critical" or "Error" that happened right before each restart. Click on one and read the details in the pane below. Look for text that mentions a driver name (like "nvidia.sys" or "realtek.sys"), a program name, or a specific error code. If you see the same driver or program name before each restart, that is your culprit.

If the log shows "The system has rebooted without cleanly shutting down first," Windows is crashing but not telling you why. In that case, look for "Kernel-Power" events with error code 41, which usually means a power supply problem, overheating, or bad RAM. If you see "Driver Irql Not Less Or Equal" or similar, a driver is corrupted.

Uninstall or update the problematic driver or software

If the Event Viewer log pointed to a specific driver, go to Device Manager by pressing Windows key + X and selecting "Device Manager." Find the device that matches the driver name (for example, if the log said "nvidia.sys," find "NVIDIA" under Display adapters). Right-click it and select "Uninstall device." Restart the computer.

After the restart, Windows will reinstall a basic version of the driver. Then visit the manufacturer's website—NVIDIA, AMD, Realtek, Intel, or whoever makes the device—and read the latest driver for your exact hardware. Install it and restart again. If restarts stop, the old driver was corrupted and the new one fixed it.

If the log pointed to a program instead of a driver, uninstall that program through Settings > Apps > Apps & features. Find it in the list, click it, and select "Uninstall." Restart and see if the problem stops. If it does, the program was causing the restarts. You can try reinstalling a newer version from the publisher's website, or contact their support to report the problem.

Run hardware diagnostics or reinstall Windows

If you have ruled out updates, overheating, and software conflicts, the problem is likely hardware failure or deep Windows corruption. Most computers come with a built-in diagnostic tool. Restart your computer and look for a message during boot that says "Press F12 for diagnostics" or "Press ESC for startup menu" or similar. Follow the on-screen prompts to run a memory test and hard drive test. These take 10 to 30 minutes.

If the diagnostics find errors, the hard drive or RAM is failing and needs replacement. If diagnostics pass or you cannot access them, try a clean Windows reinstall. This erases everything on the drive and installs a fresh copy of Windows. Back up all your files first—use an external hard drive or cloud storage. Then go to Settings > System > Recovery and click "Reset this PC." Choose "Remove everything" and follow the prompts. This usually stops restarts caused by corrupted system files.

If restarts continue after a clean reinstall, the problem is almost certainly hardware: a failing power supply, bad RAM, or a failing hard drive. At this point, take the computer to a repair shop for diagnosis, or contact the manufacturer if it is still under warranty.

Frequently Asked Questions

My computer restarts every time I try to play a game. What is happening?

The game is pushing your GPU or CPU hard, and the computer is overheating and shutting down to protect itself. Clean the dust from your fans and vents, make sure the computer has good airflow, and read a temperature monitor to confirm. If temperatures are normal, the game may be using a driver that is outdated or corrupted—update your graphics driver from the manufacturer's website.

I see a blue screen with an error code before the restart. What does that mean?

The blue screen (called a "Blue Screen of Death" or BSOD) means Windows crashed and is about to restart. Write down the error code or take a photo of it. Search for that code online along with your Windows version—it will usually point to a specific driver or hardware problem. The Event Viewer log will also record the crash, so check there for more details.

Can malware cause random restarts?

Yes, malware can force restarts as part of its behavior or to prevent you from removing it. Run a full scan with Windows Defender (built into Windows) or read Malwarebytes and run a scan in Safe Mode. If malware is found and removed, restart normally and monitor for further restarts. If restarts continue after malware removal, the problem is something else.

My computer restarts every night at the same time. Is that normal?

That is almost always a scheduled Windows Update. Check Settings > Update & Security > Windows Update and look for a "Restart options" or "Active hours" setting. You can set active hours so Windows will not restart during times you are using the computer. Windows will still restart, but it will wait until outside those hours.

Do I need to replace my power supply if restarts keep happening?

Not necessarily. Run the hardware diagnostics first to see if they detect a power supply problem. If diagnostics pass and you have ruled out overheating and software, the power supply might be failing, but it could also be bad RAM or a hard drive. A repair shop can test the power supply with a multimeter to confirm before you buy a replacement.