my asus maximus V1 hero was doing the same / similar thing, but not from power plug disconnected, or power button in off position, wouldnt boot, then would boot loop 3-4 -5 times, turn the power off let it sit and it would boot into bios, then just shut down in bios, clrd cmos, several times, battery out and upside down, it came good then started the issue all over again, id not long had the socket replaced as i bought it with a broken pin, worked ok then started to deteriorate from 4.7 gig to 4.3 gig with a pentium g3258 in it without explanation, cpus z voltages reading low and all over the place as vcore was set to 1.45-1.5v in the bios, cpuz reading 0.77, 0.88, to 0.192 , crazy readings, removed the cpu to check and dropped it and broke a pin, well that fixed the problem good and proper, killed the board lol, as far as removing the battery for hours instead of minutes and having the clr cmos jumper on overnight to my understanding it allows the capacitors to discharge completely, i have read gigabyte are culprits for having to have the clr cmos jumper and battery out for hours as well, we have seen when you turn the power off the board still looks powered up until the capacitors release but they arent fully released of charge, thats how its been explained to me
my gigabyte EP45T EXTREME does the power on off thing over and over no matter what i do and i dont know whats wrong with it, cant see anything obviously wrong visually