PC with Windows 8 Pro keeps rebooting for no apparent reason. Event viewer does not show any apparent problems. No recent software installed. Avast Free Antivirus is installed and does not show any virus or malware.

How often do the reboots occur and is this on a domain? - FYI, Windows 8 will restart automatically by default 2 days after installing updates.

REboots occur almost everyday when I start the PC up. Sometimes they stop with 2-3 but other times (like today) the machine has rebooted at least 10-12 times. This is a home PC and not on any domain. I did think the restart was due to updates but realized the reboots and updates are not really correlated.

 

Check this:

Windows Kernel event ID 41 error "The system has rebooted without cleanly shutting down first" in Windows 8

http://support.microsoft.com/kb/2028504

This was an issue I posted sometime in 2014. I have upgraded to Win 8.1 but the restart problem still persists.

A few times I noticed the restart occurs even if I go into the BIOS screen.

I was told it may be a problem with the UPS and changed to a new 600VA one. But the problem still continues. 

One question - Would some kind of spike buster be needed even if UPS is present?