CPU / Memory suddenly hitting 100% usage

I built my PC in 2019 with pretty good specs. I'm a big gamer and consistently use my PC to play games, occasionally watch movies on a 2nd monitor, and stream. This hasn't been an issue in the past.

Recently, however, in the past few weeks i've noticed some odd things. My Twitch on my 2nd monitor will randomly freeze while playing games like World of Warcraft. When I tried playing the most recent season of Diablo 4 last week my PC kept crashing (which was odd because I played the last season a few months ago fine).

Opening up my Task Manager I noticed when playing WoW / D4 my CPU and Memory sit around 70% with just the game and Firefox open and occasionally spike above 100%. Is my PC dying? Is it a graphics card or CPU issue? Not sure whats causing this and i'm a bit worried. If my PC is dying i'd like to start building a new one now.

Let me know everyone's thoughts. Thank you!