PC sometimes doesn't post

[Potat0Sa1ad]

Hello, my PC is being weird, it sometimes starts up fine but sometimes it doesn't post and doesn't start up, after 20 seconds it turns off and 10 seconds after that it turns on a again. It either does that or boots but doesn't post and just stays on. Please help

 

[johnnyb105]

cOULD BE ALOT OF THINGS GOING ON WITHOUT A LIST OF YOUR PC SPECS its hard to pin point whats going on just a wild guess here would be PSU....