I've had my M2 Pro Mac Mini for over 5 weeks. 12/19, 32GB, 2TB.
I have never heard the fan at all before today (*). Even though I regularly use handbrake and have cpus maxed for an hour or more at a time.
Strangely, I had just finished watching a video today when the fan spun up, and was quite loud. The body was its normal cool temp, the cpus were doing nothing. It stayed on for maybe 10 minutes, then went back to normal.
iStat Menus has never shown any temp sensors since I got this thing (**), so couldn’t tell if something was high. I tried its option to reset sensors to no avail. After this episode today I uninstalled it and re-installed, and now I have all the sensors availble to view. So if this happens again I’ll have something to look at.
After it was back to normal, I used handbrake to transcode a video, it took over an hour, and the body was quite warm, but the fan was never loud enough to hear.
Can’t figure out what caused this.
* I have a large-ish aquarium 6 feet away that circulates >900 gallons of water per hour, so it's not really quiet in here.
** I migrated from an M1 mac mini, so there must've been some M1 remnants in the iStat Menus config that goofed it up.