As others have said, it’s probably overheating.

That’s a mini, and likely doesn’t have any fans at all (or something perfunctory), so probably won’t handle being run at high cpu for more than a few minutes.

I currently have a small-form-factor pc with the same issue - drive and general box temps were high (drive was 110f, continuous, within range but on the edge). It would randomly reboot.

Replacing the paste on the cpu cooler helped a lot (no more random reboots), but adding a compressor-type fan dropped box temps (and more importantly drive temps), down to room temp.

I think the best you may be able to do is add an external compressor fan with some duct tape.