if you custom built this computer then perform this task.
Shut down your computer turn off the power to the computer at the the switch then open your casing.
Go to where the memory sticks are or DDR rams slots pull out all the ram sticks and put them back one at a time and as advised by your motherboard manual and start the computer each time and see how the computer runs before putting the next ram back in the slot.
If that does not help check your bios configuration pay attention to how memory or ram is configure in the bios settings and check it against the manual and or manufacturer webpage recommendation.
Finally if that does not solve your issue look at:
Checking your fan settings in bios (hot computer will cause system freezes) consider getting liquid fan cooler if you do not have one already.
Modern computers really need those cooling fans on the cpu weird as it sound but that what happen to me 6 months ago on my z490 computer had it for 9 months running 6 basic fans nothing wrong until one day i decide to add gaming monitor then all my problems started.
Now running liquid cooling fan on the cpu only after chatting to computer store owner ruling out basic issues and computer viruses to my surprise no issues with lock ups, slow and drain on the system when using it. my temperature for the graphic runs at 70 Celius the cpu around 35 degrees which amazes me.
CPU with the new graphic card use to get up to 100 degrees and shut my computer down in the end but fixed that with cpu liquid cooling fan only.
Other things to consider:
Possible software issues and conflict starting.
Possible other hardware is faulting under load
Windows defender settings and schedule scans times are causing it.
Services settings under Administrative tools virtual disk is stopped restart it and make system restore point then restart your computer.
Other computer users in your home on the internet at same time watching movies or downloading stuff causing your bandwidth to slow down which is causing Windows 11 to download and update in back ground slowly leading to unresponsive system.
Internet is connection is preventing communication between your computer is Microsoft (restart your modem as you may have gotten firmware update do this from the advance feature of your modem not manual at the button or power switch)
Computer virus has some how enter your computer (check for it and deep clean as necessary)
Worst case someone is actually taking control of your computer at concern time and play games with you (if that is the case change your password in modem after chatting with your internet service provider the one who supplies you the modem and internet service reason they may want to monitor the situation and see who is doing it and put a full stop to it.)
