Thanks, I have done that and it's my current shuffle setting in the app when I have shuffle on.
The problem is that the android auto car interface defaults to "all songs" when you hit "shuffle" at the top of a playlist. Ideally, that one tap would just shuffle all songs in that playlist, but instead, I have to select a song, then go into the menu and hit shuffle twice for it to shuffle how I want. It's too many taps for an interface that's meant to be distraction free.