PC restarting after 3 minutes

Hello everyone,
I've heard good things about this forum so I figured I'd give it a try. My PC has a problem of restarting after a few minutes, no matter what I do. I know it is hardware related because I have even tried sitting in the BIOS menu for 3 minutes and it still restarts. Actually it doesn't quite restart, it shutsdown and displays what was last on the screen but all jumbled up. I have to hold down the Pwr button to shut it off. Sometimes when it does this my monitor will say "cannot display frequency ". When I access BIOS again, the CPU temp is average, like 38*C. Please HELP ME!!!!

 

Cool. I was thinking that after reading some other forums. I think that will be my next plan of action, switching out the p/w supply. I thought it was the mobo, but the p/w supply would be alot cheaper to try. I'll let you know what happens. Thanks.