Hi,
I have the same issue and it started somewhere around the time I started playing with the colors of the RAM.
I have a Ryzen 5 7600, Corsair Vengance 32 GB DDR5 6000 MT/s RGB, RX 6800, MSI PRO B650-P WiFi.
The PC will either not POST or will do so after multiple restarts and after 20 min. It will also not come out of "sleep".
My CPU and DRAM lights are on. The mobo was in waranty so I exchanged it, got new RAM again Corsair Vengance 32 GB 6000 MT/s but no RGB this time, but it won't POST again.
Did you figure out your issue?