Hi- I have the bluetooth hands free car connect/disconnect issue. I don't use media streaming, just hands free.
My main car is a 2009 Audi so I thought perhaps it was the age of the car but recently I had a brand new VW Golf hire car and it is exactly the same if not worse ( or perhaps I just notice it more because the car infotainment display is better )
I have a new iphone 8. My previous iphone 5s was 100% reliable. I have upgraded each version of ios 11 but to no avail, it remains the same.
A colleague has a more recent iphone 8 ( about 2 weeks newer ) and has no problems with his 2009 Audi bluetooth, yet- he is on the same ios 11.0.3.
I have found one trigger in my 2009 Audi which is that bluetooth connects automatically when the car is first started and appears to be a solid connection ( no connecting/disconnecting) until the first time I select 'numbers dialled' in the car and then it immediately disconnects, the menu says auto-connection is taking place, and it goes through the whole connect/disconnect process. Eventually is calms down, stays mostly connected and has not yet dropped connection mid call.
Hoping for a fix soon- and that it is not a phone hardware issue....