What phone?
What model year? (2015-17 style or 2018-19 CarPlay/AndroidAuto)
I've been using Pandora with the Starlink head unit and iOS (iPad mini 4 in the Legacy, iPhone 7 in the WRX) for 3+ years now. It's occasionally glitchy, but works 99% of the time.
Restart your phone daily! I turn mine off every night and then plug it in to charge so it powers back on. Same effect as restarting your PC.
Open Pandora before connecting to the car. If this doesn't work, connect first and then open Pandora on your phone. Or connect then use the head unit's Pandora button to launch. If it doesn't work just change to another sequence.
I just upgraded from Pandora Plus to Premium, which lets you download stations and custom playlists. Both show up in the station selection list on the head unit, pretty cool. Lost the unlimited data I had on my iPad so offline mode is a must now.