Since the Marshmallow update, my G3 randomly restarts several times a day (10 or more plus I hear it sometimes on my nightstand). Sometimes when I am streaming to a Bose Mini, sometimes watching a Video, sometimes playing a game, and sometimes doing nothing while it is just sitting on my desk, so I'm sure it is not an app problem. I called customer support and the guy was great, he really tried and spent probably close to an hour trying to help. We tried the upgrade tool on the PC, and everything went smooth until it said Repair Phone. The repair section showed the phone connected, and I could high-lite it, but the repair button is inactive. I even sent him a screenshot, because I figured he thought I was computer illiterate, which I ain't... And he couldn't understand. He even said, that this program was purposely made to be as easy to use as possible.
Anyway we went through all the options he could think of with no results. I had things to do so we just quit trying.
It still restarts all the time. The phone also seems to get warm, and the battery seems to drain more rapidly than I had noticed in the past.
My suspicious mind even thought that, since the contract is nearly up on this phone, that V put a bug on it, so I would be more likely to upgrade, instead of keeping a phone that I am perfectly happy with. I am sure they wouldn't do that, but it's just the timing of it that started me thinking. I saw the upgrade and thought "Awesome, my phone will be even better now." Installed it, and now don't know if I could trust it in an emergency.
Anyway if anyone knows what to do, please let me know, and if anyone is having the same problem, please chime in so they might work on a solution.