Good Afternoon Pete my name is Stason,
I know of two ways to do this. If your car will do it, you can turn off auto play from your cars menu system. That may or may not be possible depending on the car. They other way to do it is turn cellular data off on the music app. To do that go to setting -> Cellular -> and scroll down to "Use Cellelar Data for'.. Scroll to the Music App and slide the slider to the left to turn it off. That should stop auto play when your phone connects to your car.
Do you need anything else today?
Ill try those, thanks