my desk top computer keeps shutting off and turning back on

Unexpected shutdowns and automatic restarts are commonly caused by a hardware device, its driver, software, or a power problem. For this pattern, use this order:

1. Check whether Windows logged Event ID 41
   Open Event Viewer after the restart and check Windows Logs > System. If Event ID 41 appears, it means Windows detected that the PC rebooted without shutting down cleanly.
2. Interpret Event ID 41 carefully
   If Event ID 41 isn’t recorded, or if it is recorded but BugcheckCode and PowerButtonTimestamp are 0, that can indicate:
   • interrupted power
   • a faulty or underpowered power supply
   • the PC became unresponsive and was powered off too quickly to write error details
3. Check for related events around the shutdown time
   In Event Viewer, look in both Application and System logs for suspicious events just before the shutdown time. The shutdown time can be identified from Event ID 6008.
4. If the PC freezes before restarting, test for a hard hang
   Press Caps Lock when the issue occurs. If the keyboard light does not change, the computer may be unresponsive.
5. Turn off automatic restart so stop errors can be seen
   If the PC is showing a stop error too briefly to read:
   • Right-click My Computer
   • Select Properties > Advanced system settings > Advanced
   • Under Startup and Recovery, select Settings
   • Clear Automatically restart
6. Try the basic Windows recovery steps
   If the restarts continue:
   • Remove any newly added hardware
   • Start the PC in Safe Mode
   • Open Device Manager from the Start button and check for devices with an exclamation mark; update, disable, or uninstall the affected device if needed
   • Make sure the drive has about 10% to 15% free space
   • Install the latest Windows updates from Start > Settings > Windows Update
7. Use recovery options if needed
   If none of the above helps, use Windows recovery options. Important: some recovery options can result in data loss, so back up important files first.

If the machine restarts before Windows can log useful details, the strongest indicators in the available guidance are a power interruption, faulty/underpowered power supply, or a system hang preventing Windows from writing the error information.

References:

• Advanced troubleshooting for Event ID 41: "The system has rebooted without cleanly shutting down first"
• Troubleshooting Windows unexpected restarts and stop code errors
• Recovery options in Windows