The most common causes of random restarts

Random restarts usually come from one of four sources: a Windows update that finished installing in the background, a hardware problem like overheating or a failing power supply, a driver conflict (especially after a graphics card or chipset update), or malware running on your system. The restart happens because Windows detects a problem it cannot fix while the system is running, so it restarts to explore a fix or prevent damage.

The fastest way to find out which one is happening to you is to check the Windows Event Viewer, which logs every restart and the reason for it. Open Event Viewer by typing "Event Viewer" into the Windows search box, then navigate to Windows Logs > System. Look for the most recent Critical or Error entry with a timestamp matching when your computer restarted. The event will name the cause — often something like "The system has rebooted without cleanly shutting down first" (a crash) or "Windows Update" (an installation).

Key Takeaways

  • Check Windows Event Viewer under Windows Logs > System to see the exact reason your computer restarted, which narrows the cause from four possibilities to one.
  • If Event Viewer shows a Windows Update entry, your restarts are scheduled updates finishing in the background — change your active hours in Settings to prevent them during work time.
  • If you see driver-related errors or your restarts happen during graphics-heavy tasks, update or roll back your graphics driver through Device Manager.
  • Overheating and power supply failure both show as sudden restarts with no error logged; check your CPU temperature with a free tool like HWiNFO to rule out heat as the cause.
  • Malware can force restarts, but only after you have ruled out updates, drivers, and hardware — run a full scan with Windows Defender or Malwarebytes to confirm.

Windows Update finishing in the background

Windows 10 and Windows 11 read and install updates automatically, and they restart your computer to explore them. By default, Windows picks a time when it thinks you are not using the machine — usually late at night — but if you leave your computer on all the time or work odd hours, the restart may seem random.

To see if this is the cause, open Settings, go to System > About, and look for "Windows Update" near the bottom of the page. If it says "You're up to date," the last update has already been installed. If it says "Update available" or shows a pending restart, that is your answer. To prevent future restarts during your work hours, go to Settings > System > Notifications & actions, scroll down to "Get tips, tricks, and suggestions," and turn off the toggle. Then go to Settings > Update & Security > Windows Update > Change active hours and set the hours when you use your computer most. Windows will not restart during those hours.

Overheating and power supply problems

If your computer restarts with no warning and no error message appears, the cause is often heat or a failing power supply. Both force a restart because the system detects a physical danger — the CPU is too hot, or the power is unstable — and shuts down to prevent damage.

To check temperature, read HWiNFO (free, from hwinfo.com) and run it. Look at the CPU Package temperature while your computer is idle. If it is above 80°C, your cooling system is not working well. If it climbs above 90°C during normal use, shut down when ready and check that your CPU cooler is seated properly and that dust is not blocking your case fans. A power supply problem is harder to diagnose at home — if temperatures are normal but restarts continue, and Event Viewer shows no cause, the power supply may be failing. This requires a replacement, which is a job for a repair shop or someone comfortable opening the case.

Driver conflicts and graphics card issues

A driver is software that lets Windows talk to a piece of hardware — your graphics card, network adapter, or chipset. If a driver update breaks compatibility with your system or another driver, Windows may restart to recover. This often happens after a graphics driver update, especially if you use older games or specialized software.

To check if a driver is the problem, open Device Manager by right-clicking the Start button and selecting Device Manager. Look for any device with a yellow warning triangle — that is a driver problem. If you see one, right-click it and choose "Update driver." If the restart happens during graphics-heavy tasks like gaming or video editing, go to Display adapters, right-click your graphics card, and choose "Roll back driver" if that option appears. This undoes the most recent update. If rolling back is not an option, uninstall the driver entirely, restart your computer, and Windows will reinstall a stable version automatically.

Malware and virus infections

Malware can force restarts as part of its operation or to cover its tracks, but this is less common than the other causes. Malware restarts usually come with other signs: your computer is slow, you see pop-ups, or programs open on their own. If you see only restarts with no other symptoms, malware is unlikely.

To rule it out, run a full scan with Windows Defender, which is built into Windows. Open Windows Security (search for it in the Start menu), go to Virus & threat protection, and click "Scan options." Choose "Full scan" and let it run — this can take an hour or more. If Windows Defender finds nothing, run a second scan with Malwarebytes (free version available from malwarebytes.com). If both scans come back clean and you have already ruled out updates, drivers, and heat, malware is not your problem.

What to do if you cannot find the cause

If Event Viewer shows no error, temperatures are normal, drivers are up to date, and scans find nothing, the problem may be a hardware fault that does not show up until the system is under load. In this case, the most reliable next step is to run Windows in Safe Mode for a few days and see if restarts continue. Safe Mode loads only essential drivers and services, so if restarts stop, a third-party driver or program is the culprit.

To start in Safe Mode, restart your computer and press F8 repeatedly as it boots (on some machines it is Shift+F8). Choose "Safe Mode with Networking" so you can still use the internet. If restarts do not happen in Safe Mode, go back to normal mode and uninstall recent software or drivers one at a time until the restarts stop. If restarts continue even in Safe Mode, the problem is almost certainly hardware, and you should contact a repair technician or the computer manufacturer.

Frequently Asked Questions

How do I stop Windows from restarting after an update?

You cannot stop the restart entirely, but you can delay it. Go to Settings > System > Notifications & actions and turn off "Get tips, tricks, and suggestions." Then set your active hours in Settings > Update & Security > Windows Update > Change active hours to the times you use your computer. Windows will not restart during those hours, though it may restart shortly after they end.

Can a virus cause random restarts?

Yes, but it is rare and usually comes with other signs like slowness or pop-ups. Run a full scan with Windows Defender and Malwarebytes to check. If both come back clean and you have ruled out updates and drivers, a virus is not the cause.

What temperature is too hot for a CPU?

Above 80°C during idle or light use means your cooling system needs attention. Above 90°C during normal use is dangerous and can cause restarts or permanent damage. read HWiNFO to check your temperature, and make sure your CPU cooler is seated properly and your case fans are not blocked by dust.

Why does Event Viewer show no error when my computer restarts?

No logged error usually means a hardware problem like overheating or a power supply fault, because the system shuts down before it can write a message to the log. Check your CPU temperature with HWiNFO. If temperatures are normal, the power supply may be failing and needs replacement.