You need to downgrade your Spotify version to 22.214.171.1249 not the latest one from the Play Store (then untick auto-update). I had the same issue on my brand new BMW and this fixed it. It now connects every time I get in the car perfectly.
I have a 430i with ID5; same issue, Spotify worked happily till early November. After much playing around, I've found that Spotify App 126.96.36.1990 is the latest version of the App that still works with BMW I-drive, or at least with the ID5 version.
.530 works fine, and I'm now waiting patiently for Spotify to fix the BMW integration.
There is penty of info on the bimmerpost forums on how to roll the app back; just remember to turn off auto update for Spotify in your playstore settings or you will be back to no go again.