CPU spiking suddenly on games that worked fine before and BSODs

I built this PC last summer. It was my first time doing that and I had no idea what I was doing.

Specs:

Windows 11 Home

13th Gen Intel(R) Core(TM) i9-13900KF 3.00 GHz

AMD Radeon RX 7900 XT

Intel 660p Series M.2 2280 1TB PCIe NVMe 3.0 x4 3D2, QLC Internal Solid State Drive (SSD)

Crucial 16GB DDR5 5600

Seagate BarraCuda 2TB Internal Hard Drive HDD

For the first 6 months or so there were relatively few problems with my computer and games ran great. Recently, I started having problems with Rocket League suddenly crashing while trying to join a match. Sometimes this happens on the first try, sometimes I can play a few games normally and then it will randomly crash, usually while joining a match, but sometimes in the middle of gameplay.

Recently, I've noticed that I can't even get some games to start anymore, including games that ran fine just a few months ago. For example, I played through Hogwarts Legacy on high settings several months ago with no issues and now when I try to start the game with Task Manager open, the CPU immediately spikes up to 100% and the game crashes in like 5 seconds before even getting to the menu. This is happening with other games too including Rocket League sometimes. Occasionally, the whole computer crashes and I get blue screens with codes like CLOCK_WATCHDOG_TIMEOUT.

What I've done so far is basically everything it says in this article:

-Checked drivers. Everything is up to date as far as I can tell.

-Uninstalled and reinstalled games. Reduced graphical settings.

-Scanned for malware. Nothing.

-Checked hardware. Granted, I probably don't know enough about computers to notice if something minor was installed incorrectly by me (entirely possible because again, I did my best to follow instructions, but I had no idea what I was doing), but I cleaned out some dust, made sure fans were spinning, checked plugs, etc. Couldn't find anything obvious wrong.

I'm at a loss. I haven't made any major changes to this computer that could explain this. It just started having problems seemingly out of nowhere. Any advice you can give me as far as next steps or other things I can try would be greatly appreciated.