I'm loving this message, only cos it shows me that I'm not the only one who gets annoyed by this.
Everytime I get in my car it starts on the last radio station I was listening to, within the first 30 seconds it will switch to airplay, specifically Spotify.
I am on wireless airplay and have tried disabling this only to find that after a few journeys it magically turned itself back on and repeated the self switch again.
I have spoken to my local service department who say they don't know about it and insinuated I was the only person to mention this issue, hence my first sentence.
Good luck on resolving this, I'll let you know if I get anywhere.