iMac (Loud Knock Sound) Freezing & PRAM Restart Issue

I have recently purchased a 2019 iMac. I updated the RAM with OWC 2x16gb sticks and I am also using the factory 2x4gb sticks for a total of 40gb.

Freezing Issue

On day one of having the computer I was just browsing the web and installing apps when the a extremely loud knock sound came out of the speakers and the iMac froze for about 5 seconds and restarted. This happened several times and I called Apple Support they directed me to reset the System Management Controller (SMC). I did that and it seemed to fix the issue. Then it happened a few more a couple of days later and I reset the (SMC) again. This seem to stabilize the computer for about a month and half. Then I updated to Catalina and the problem started all over again.

PRAM Reset Issue

In an effort to try and fix the freezing issue I tried resetting the PRAM. When I hold down the keyboard shortcuts after restart, I see the Apple logo once then the screen goes black and doesn't ever come back. The iMac is still on because the fans are still running. In order to get the screen back up I have to reset the (SMC) 2-3 times before the screen comes back up.

Any help or anyone also else having this issue and has more info, it would be appreciated.