回答“Mac keeps restarting for no clear reason.”I disagree with the power supply diagnosis. Unless you have set your power save options to restart after power fail, the machine will stay off. Mine does not stay off. None of the others reporting this issue claim it stays off. I was having the random restart problem several times per day after updating to High Sierra. The suggestions above caused me to start thinking about what functionality might change across releases. I decided to look at Power Save options. I disabled power save for both system and display (set it to Never). The problem has disappeared. I have been running for a week now without recurrence. It appears that Apple has introduced misadventure into the Power Save behaviour of (at least) High Sierra on Mid-2011 Mac Minis.