Well it's either a POST issue or a CPU heat issue (thermal paste becoming less efficient).
I had/have that problem with the motherboard chipset, thermal w/e issue.
I leave my comp on 24/7, but every now and then for various reasons, I shut it down for a day or so. I noticed that w/e thermal solution they used on the chipset, would contract when it completely cooled down, and then would cause boot issues when I managed to restart the comp.
After a few tries to start the comp, I assume it would heat up just enough to "flow" again, and remove the problem that cooling/contracting caused.
This post was edited by Ghot on Apr 4 2018 06:53am