Pc turning on for a split second then turning off

[whiteoral]

So i built my pc yesterday and got the drivers and everything and it was working 100%. I left it on overnight to download some music. When I woke up in the middle of the night it was turned off, so i tried to turn it back on but it shut off again after a second, so I just went back to sleep. In the morning, it was continually shutting on and off. On for a about half a second, then off for about 5 seconds, repeat, until I unplug the cable. Every fan inside goes on for that split second.

8800gt
520hx
e8400
4gb gskill
antec 900
xigmatek cpu cooler
320gb maxtor
ep35 ds3l

Any ideas?

 

[tiraides]

Try running the motherboard outside of the case. If it works, then chances are that you may have a short inside the case.

Are you using a surge protector or an UPS to power this machine with?

 

[MrGuvernment]

remove all parts except

CPU / Ram / Vid card

everythig else OUT - see if it is shorted
if it powers up then, add other items in one at a time... could be a bad PSU, that is usually what happens in the case of a under powered system, but you got a decent PSU...

 

[Koslov]

Most likely mobo or PSU problem.
Are you running the latest bios>?