My Raspberry Pi 4 started running hot when I moved it from a freestanding case to a fanless server rack. I’d often SSH in and see idling it at 65C or warmer, with log messages showing it had been thermally throttled. That’s not great.
I just bought a Argon Fan HAT. I installed it and fired up a large Rust compile with 4 concurrent jobs. 20 minutes later and the RPi averaged about 54C with no throttling.
Get your Pi a fan. It wants one very much.