Computer repeatedly turns on and off.

Possible things off the top of my head:

Bad piece of main components
Bent Motherboard pin under CPU
Bad RAM or ram slot
Bad PSU(if it turned on, i don't expect it be this)
Motherboard BIOS compatability (only fixable with older cpu bios flashing or changin motherboards)


here's generic guide list


I would also try a CMOS reset(look in motherboard manual for instructions, usually either a switch or the battery method) in case of some odd settings