Reboot the system and start tapping F12 immediately. Run full diagnostics and watch for any errors, particularly drive errors as the HDD/SDD could be giving you problems.
 I have a Dell optilex 390 series, Intel core i3 processor with 500gb HHD, 8gb ram, indtwllin with a new windows 10 update 2021. The issue is that my computer is freezing randomly when used for a few hours. This used to happen when I had the old version of Windows 10, so I updated it but I'm still getting the some problem. And I've tried reinstalling Windows, updating drivers, installating anyivanti but still get the some freezing problem. The temperature of the CPU is running around 50-70 when I'm not doing anything. Please help me of how I can make this problem go away. 
Dell optilex 390 series