My desktop pc keeps shutting down/freezing/rebooting itself (even in BIOS) in the first 10-20 minutes of activity, after that time it works properly.
I looked into the windows event register but there's nothing except "abnormal shutdown", and that doesn't help. I did a scandisk and a RAM check but everything was okay (the RAM check was canceled the first two times because the pc freezed, then at the third attempt it completed successfully)
What could it be? Can you suggest some tests to diagnose the problem?