If you have the other RAM installed along with that 16GB stick, that could be causing the problem. Mismatched RAM can cause all sorts of strange issues.
It may not have been the RAM. Because removing the new RAM had it doing the same thing. Despite it previously working fine on the dual monitor setup.
I remembered when I was in the PC, I brushed out a LOT of dust from the fans and processor with a Keyboard brush. So i was thinking maybe a clump of dust lobbed into the wrong spot.
But I also remembered there was a JUMBO fan on the side of the tower case that was unplugged and I’d plugged it in.
But once I unplugged that one fan its working good as of now, so far anyhow