Question PC just froze and became slow responding

[frozensun]

Hey friends.

Well I'm so sad,my built rig is apperently sick.

I was watching youtube video when suddenly picture froze,got black screen,and PC became unresponsive.

I move the mouse but nothing happens,or cursor moves with huge delay.

My rig:

3900X not OC

Asus Crosshair Hero VIII,

Corsair Vengeance RGB 2x8GB DDR 4 CL 16 DOCP enabled

Corsair HX1200i

GPU:Asus Strix 1660 Ti OC (not OC)

Cooler:Corsair H100i.

I haven't been on this computer a lot,I did play some Doom Eternal like 2h max and had no issues.
I checked temps and all seem fine.
What to do?What to check first and what could be the cause of problem?
problem:

View: https://www.youtube.com/watch?v=cajDNyzvs5s

 

[Lutfij]

You might want to go into BIOS and see if your temps are being reported the same as what you're seeing in OS. I'd probably look at the BIOS first, see if there are any BIOS updates pending, then look at the OS to see if there's any updates pending as well. If you've got nothing important on the OS installation drive, I'd advise on reinstalling the OS.

Create your bootable USB installer using Windows Media Creation Tools.

Please include/list your specs like so:
CPU:
Motherboard:
Ram:
SSD/HDD:
GPU:
PSU: age of the unit
OS: version

 

[frozensun]

tested the rig with Aida64 stability test for 6 hours no issues,tested RAM with memttest86 no issues,checked temps in BIOS all under normal...what do to next?žI'm not updating BIOS since power failures are common in my city and I don't own UPS,