System turns on, off, on...



I've built a PC sometime back in April, and despite a few now fixed BSODs it worked fine. However, recently (probably two days ago) I've noticed that my computer will turn on, off, on, off and then back on again. After which it operates PERFECTLY FINE.

What could be the problem? I haven't changed any hardware, haven't downloaded any suspicious software (or any at all in the past week), did not get some sort of critical error. I'm afraid this could just be the beginning of a bigger issue.

My specs:

P8Z68-V PRO/Gen3
GTX 680 2GB (not OC'd)
i5-2500k (OC'd at ~4.6 GHz, but everything has been stable for months)
8GB RAM DDR3 (two sticks running @ 1333 MHz, downclocked from the unstable 1600 MHz)
Corsair TX850 V2.

Thank you in advance.

make sure your mb has the newest bios there been some updates for same and usb and video cards for the x68 and z77 chipsets and windows 7/8. the newest bios there two of them one for xp and one for windows 7/8 3603. after you install the newest bios make sure xmp profile in the dram speed is turned on. on asus mb be care full on clicking overclock in the easy bios setting most time asus overcloker will change the cpu/ram timing. in standard more it set to 1:1 on the high end over clock it changed to 1:5 and can make system unstable.