I vaguely remember reading about this issue in the past, it’s actually down to the way the software running in the cars radio is using a backwards compatible “iPod” integration. It effectively (against Apple’s recommendations) sends a “play music” signal as soon as you connect your device.

Well behaved radios don’t send that signal immediately, and instead wait for you to hit play on your device, or on your cars radio/stalk.

Nothing to do with Apple, but I recently bought an old car. It has a radio. Whenever I turn on the engine, it switches on. Actually, no, it doesn't switch on, because I found that behaviour so annoying that I just unplugged the whole thing from the power. It's a fancy sat-nav touchscreen radio that can show a reversing camera, has loads of settings menus, but doesn't have an option to stop it being stupid. What gives? Who in the industry thought that this was what people really wanted?

> When I plug it into the car, it automatically starts playing the same song on Apple Music

My car (maybe most?) helpfully sends a "play" command when my phone connects via Bluetooth. iOS devices play what was last playing, or pass the event to your music app if you've played something else in the meantime.

The fix in my case was a Shorcuts automation that gets triggered when the phone connects to your car. I set the volume to max and tell my favorite podcasts app to "Play".

If I just wanted an app to always be considered the "last played" app, I'd do something like add a one second delay and then pause. If I used Spotify, I'd also delete Apple Music.

Reminds me of this gem: https://news.ycombinator.com/item?id=32163667

That sounds like a bug. Mine autoplays tidal, overcast or nothing, depending on what I was listening to last.

I even trained siri to use tidal by saying “play artist on tidal” a few times. (Siri is completely useless for this use case, but it does not open apple music.)