I have the same issue with my bluetooth connections. I suspect this issue pertains to the introduction of low energy BT. My biggest problem resulting from this tech glitch is that just like how car bluetooth connects and disconnects repeatedly, this same scenario happens with my Oticon Hearing Aids. I can't use the one function that I spent lots of money on a streamer device to facilitate this-using my hearing aids as a bluetooth headset for phone calls.
I can also connect these Aids to my phone to use with the GPS functions of my phone. This also disconnects and reconnects repeatedly. Here's why I believe the issue has to do with BT low-energy functions: I discovered that if I start streaming music (Spotify/Pandora), THEN open Waze and set my route, I no longer lose the BT connection for the use of GPS. Hmm, looks like streaming audio uses the hi-power BT connection, while phone and GPS uses the lo-power?
BTW-I have spent HOURS connected with Apple in this regard, and followed every recommendation. There is no fix, and no further info (not even encouragement that Apple realizes that this is an issue, or that they're working on it for a future fix). Looks like the fix is to go back to Android.