I have been having the same issue with BT switching itself off for about a week now. Never had any BT issues prior to that. Mine is a Verizon Pixel XL. I noticed it when it wouldn't connect to my car, but I quickly discovered that was because BT was off on the phone. I always leave BT on, so I knew something was funky and paid close attention after that. Once I turn it back on it connects to everything just fine and it stays on for the duration of me using it at that time. But when I go to use it the next time, it is off again. It can be a variable length of time in between when I use it, so I don't know how soon it turns off, but it has to be within just a few hours. This pattern suggests to me that something is turning it off, perhaps to save battery, if it goes without being used for a certain time period. I did not knowingly turn on any setting that does that, so it makes sense that an update changed something. I have not tried the workaround/fix mentioned above; I will do it and report back.
