Yes, my Series 3 Apple Watch suddenly quit on me. But I fixed it. It cost me nothing and I didn’t need any tools.
The key to this fix was a proper diagnosis. The clue here was that “Erase all content and settings” looping message. That strongly suggested a stuck power button. And indeed, the power button felt stiff and sluggish. In fact, it had been feeling a bit “off” for some time, something that I noticed when I tried to use Apple Pay.
OK, so the button was stuck. But how to unstick it? Prying it with a Swiss Army Knife, or trying to pull it with pliers seemed destructive, and liable to leave “memories” of the endeavor in the finish of my Apple Watch.
My second thought was to squirt a little lubrication around the button, something like WD40. But alas, my travel kit did not include WD40. Also, I don’t like exposing rubber gaskets to petroleum sprays (silicone sprays are better, but I didn’t have any of that either).
Third thought, dunk it in some warm water for a few hours, and jab at the button repeatedly to see if it would loosen up.
After about an hour in warm water — I took a chance here that the waterproofing was still up to the job of a prolonged swim in warm water, but since the watch was already non-functional, and I didn’t have any AppleCare warranty, I didn’t feel I had much to lose — I worked the button, and to my surprise it was back to feeling normal.
I threw the Apple Watch back on a charger and set it up, using the last backup I had before the erasing loop, and had it back on my wrist in a few minutes.