If I don’t have any audio app up and ready to play, mine will start playing a podcast – the podcast app isn’t even running in the background. If I have another audio app up it won’t do that. Anymore, I just start listening to something and then when I get in the car that’s what will play.
if I have Spotify up and music paused, I don’t think it will play until I unpause it, but maybe it does. I forget – I’m usually listening to that and it just switches to the car when I get in. Podcasts will start playing as soon as the phone connects if nothing else is going on the phone, likely that was the last thing I was listening to At that point.
I figure it’s an iphone thing – apple still doesn’t have a setting to toggle auto play with either the Bluetooth or the CarPlay settings. Been doing it for many versions of the iOS now.