Z170-A starts and stops over and over?

This is a motherboard that I bought as "open box" from eBay and I've had mixed success buying such motherboards:

In this instance the board came without the cpu socket cover so the first thing I did was use a flashlight and magnifying glass to carefully examine the cpu sockets pins and I'm 100% certain that there was no damage or bent pins before installing the cpu and heatsink.

I have the motherboard setup on a testbed and the second that the power supply is turned on the motherboard starts without me pushing the power switch I have connected to the power switch header pins. I have two green status lights, the cpu fan and the led lights on the Corsair Dominator ram go on for 2-3 seconds and then go off for 1 and then that repeats over and over.

I get no post or video, nor can I turn it off with the power switch. I've tried two different power supply's just in case but I know they are good because the Antec PSU tester I have says they are giving the correct voltage on all pins. I'm also reset the cmos several times and that doesn't seem to make any difference.

Has anyone seen a problem like this? Is the motherboard bad?