Today this happend to me too. Felt the force feedback from my Ultra2 and noticed it was taking pictures via mij iPhone! I took the watch off, saw the screenlock being activated. Then I saw seemingly random numbers being key'd in until it triggered the 1 minute time out... I tried to deactivate the watch but that turned out to b contest of who was faster (or so it looked and felt). I turned off all connections on my iPhone (WiFi, Bluetooth). I then was able to make it to the 'turn off-' slider.
After this went online, logged onto Apple ID, removed the watch en changed my password, logged off from all devices. Back to my iPhone, updated password, reestablished connectivity, turned on the watch, went to my iPhone and to the iWatch app and factory reset the watch... now it sits there, reinstalled and waiting for pairing...
I'm going to keep it that way until this apparent leak has been plugged tight!
Hope that happens soon or perhaps there's someone here who knows more about this issue?