System Boots to Black Screen (But Not Every Time)

I recently replaced my Gigabyte z97x Gaming 5 motherboard with an Asus H97 Plus board to fix memory corruption during sleep. The new board is working fine (although I can't get the system to actually sleep anymore -- but that's another issue for another time).

My problem is that when I try to boot, the system often starts up, I see my monitor's logo on the screen and then nothing -- just a black screen and then a "no signal" message. I manually shut down by holding the power button and reboot. Half the time it will boot properly into the Asus splash screen and then on to the Clover boot menu. Other times, the black screen issue will repeat itself several times before the system finally boots.

Any idea what might be causing this and how to fix it?

My specs: i7 4770K, Asus H97-Pro mobo and a EVGA GTX 970 using Clover.