have you been able to boot up in safe mode without any problems?
I also had a restart problem when i installed a virus scanner it didnt like my pc think it was mcafee it just kept restarting my comp.
Download everest home edition to monitor temperatures:
once installed its under sensor in one of the sub menu's.
Check to see your processor fan isnt dead although that normally just causes the computer to freeze rather than reset, sounds more like a compatibilty problem with software.
If all else fails see if safemode works try and back up what you need and format but thats only as a last resort.