Good afternoon herman1964,
Welcome to the Apple Support Communities!
I understand you want to stop the Apple Music app from automatically playing when you start the engine in your car.
The feature that you are talking about is called Auto-Play. When automobiles are connected to the iPhone via Bluetooth, music will automatically start playing from the iPhone through the Bluetooth speakers when you get into the vehicle or change a setting in the stereo system.
Here are some ways you can turn off Auto-Play:
- Check the manual for your vehicle to see if there is an option to turn off the auto-play feature in the Bluetooth or audio settings.
- Quit the Music app on your iPhone before you get in your vehicle - How to force an app to close on your iPhone, iPad, or iPod touch.
- Disable cellular usage for the Music App on your iPhone - Tap Settings > Cellular and turn the switch to off for Music. Do the same for any other music apps (ie. Pandora, etc.) that might be trying to automatically connect to your iPhone.
Please reply to this thread and let me know if you are able to turn Auto-Play off using one of these methods.
Take care.