I am getting the same power cycle loop issue with a GA-Z97MX Gaming 5 and i5 4670k...except that it had been working fine for months till I restarted the computer this morning for a windows 10 update. Now its 3-5 seconds of powering up, then off, power, off in a continuous loop. I have removed all connections (usb, ethernet, audio), cleared CMOS, used one stick of ram in slot 1, removed my graphics card, tried the on/off psu switch trick, and the issue still persists. I run my business on that machine so Im freaking out a little.