I've been having an issue with Spotify automatically starting and resume playing anytime bluetooth connects to my headphones or truck. I've tried all the "solutions" that I've found listed online and none of them work, or are terribly inconvenient, like logging out or turning the settings for my Bluetooth devices to not be used for media, or restricting back ground usage (then the app won't work at all if the screen times out, which creates other problems). Since the devs over at Spotify won't add an in app option to disable it auto starting and playing in the menu (like other apps are said to have because some developers actually listen to the people who use their app). This isn't a complete solution because you still have to clear Spotify from the back ground when you're disconnecting the Bluetooth device, otherwise it starts autoplaying as soon as it reconnects. I've been having this issue since Android 8 and am currently on Android 11 on a LG V60.
In your phone settings go to: apps > Spotify > app notifications.
Tap on the playback option and change it from "high importance" to "medium importance"
Switching it to "low importance" would also work, but then you lose playback controls in the notification shade.
I've tested this with my headphones and it works, I still need to test it in my truck but am confident it'll work there too. I don't know if this is a work around if iOS has this issue or not.
I've attached a screenshot of the notification option to change, hopefully this helps someone.
EDIT: unfortunately this ended up not being a long term solution, as Spotify is now acting the same as it was before.