Mine has done exactly the same... kept recording on its own. Right top button appears to be faulty. I then let the battery run flat. Now the watch is dead !
you know which button got stuck
or
happy & safe sporting
Sounds like the battery is done. All lithium batteries have a lifetime and it's not just cycles (although that's part of it); there is irreversible chemical deterioration you cannot evade, and it eventually kills all such devices.
It is what it is.
I am sorry your watch won't power on. Use this Support Center article, Won't Power On. It mentions 30 seconds for the soft reset unplugged and then 30 seconds once plugged into charge. I recommend 60 seconds. Only for the sake of being thorough. Also, after the first soft reset, when you then plug your watch into charge, give it 10-15 seconds. It will most likely start to charge and the issue will be resolved. If it doesn't start to charge, then hold down the power button again for 60 seconds while still plugged into charge.