PC Freezes if I don't have a game running

My PC constantly freezes if I'm not playing a game or have a game running.

✅ If I'm playing a game, it's fine.

✅ If I have a game running in the background while doing other stuff, it's fine.

❌ If I leave my PC while playing a game and the lock screen pops up, it will freeze.

❌ If I do anything other than gaming, such as browsing the web or digital art, PC will freeze.

❌ If PC goes to sleep overnight, it will freeze.

The frozen PC will typically show no error code and display will show "no input" until I hard reset.

If I hard reset, it often won't successfully turn back on unless I move the mouse while it's resetting, otherwise it will freeze again on the windows loading screen.

Sometimes I will actually get a blue screen with the error code of DPC_Watchdog_Error or something like that.

Anyone know where I should look first to try and fix this? It's been happening for weeks now and it's driving me crazy. I can't figure it out.