Question CPU throttles even at low temps

[Scalinger2]

System:
(mobo) MAG B550 TOMAHAWK
(cpu) AMD Ryzen 7 3700X 8-Core 3600 Mhz
(gpu) AMD Radeon 5700 XT Mech
(ram) 2x Trident Z DDR4

Sometimes when I turn on my computer the cpu runs at ~4200Mhz, boots quick, then throttles into potato mode (~350Mhz) early or when it has a heavy load. Many times it just starts off slow and stays slow. The attached picture shows a throttling notification in event viewer. One time I was able to play Cyberpunk on ultra settings at 37fps for the entire prologue (it was working at 60 Celcius). When it's throttled down the fans are quiet and when it's working normally the fans are a lot louder. Would this be a bios setting, a thermal issue or power issue? I've had the fans set to full speed and it still potatoes while other times I've had the fans set lower and it worked fine so it doesn't seem to be a thermal issue. This is a new computer with fully updated Windows 10 and all drivers up to date.

Dropbox picture showing idle vs. performance under load:
Pic

 

[Scalinger2]

I found out the reason why my computer was being wonky was because I didn't put the rubber gasket behind the motherboard to mount the cpu water block. I just had the metal plate up against the back of the cpu.