This is how to stop music apps from playing when your Smartphone connects via Bluetooth to car

[Supersnake]

A problem that has irked various car owners for years. It recently surfaced on my car stereo, and it was driving me crazy until I came upon a deceptively simple, yet effective app, that resolves the problem.

Problem: Whenever my phone connects via Bluetooth to my car, the car sends a "play" command that automatically starts the most recently used music app (Google Play Music, Pandora, etc.). It doesn't matter if no music app was open on the phone, the command opens it up and it starts playing no matter what, and there's no way on the car to stop it from sending the command.

Solution: Install the Playstore App Bluetooth connect & Play
1. Set it to "Stop Music From Playing"
2. Set it to "0 seconds to wait after connect to play"
Set it to "no check mark for the Open Player Only option".

The Bluetooth connect & Play app is non-intrusive, does not utilize battery, and does not run in the background

Thanks go to Dan Hulme and KevinMicke for posting the problem and solution.