When my phone makes a Bluetooth connection to the car, it automatically starts playing whatever was last playing on the phone. Some people think this is a feature. I consider it a huge annoyance, for various reasons.
I finally found a solution for Android (in my case a Google Pixel): install the Automate app and run this script: Automate for Android ⋅ Prevent Bluetooth Autoplay
I finally found a solution for Android (in my case a Google Pixel): install the Automate app and run this script: Automate for Android ⋅ Prevent Bluetooth Autoplay