I have this same issue with my iPhone 12 mini. I never had any issues with my previous phone (Android). My partner also has no issues with their older model iPhone (running the same iOS version BTW). The disconnection seems to happen when I switch apps I’m using to listen to audio (Music, Audible, YouTube, Spotify, etc.). I drive a 2015 Mini Cooper and have been informed by the dealership that there are no updates for the audio system that haven’t already been installed. Apple…. this sucks.