Pc boot problem


Sep 11, 2011
i got some problems with my pc i did an upgrade of my old system
added a gigabyte 580gtx so,2x2gb ddr3, new case,4fans, a sythe mugen3 and 3hdd(one ssd) to it old parts are motherboard:ga-p55a-ud4,2x2gb ddr3,2hdd's, and be quiet straith power 700watt psu. i installed evrything like it should be.now my problem is evrytime i plug the power cable into the psu or set the switch off and on and press the powerbutton my pc starts up for 5seconds and then goes off 5 seconds and starts up again then he just boots like it should be. and it never happens again until i unplug the power cable again it happens again.i also got the feeling when gaming the pc doesnt run stable . does anyone know whats the problem?