iPhone Personal Automation Issue

PROBLEM: I want the Amazon Music app on my iPhone 11 to stream music to the media player of my 2019 Subaru Ascent seamlessly after I start the vehicle. SITUATION: I used the iPhone Shortcuts app to create a Personal Automation whereby "When" my iPhone connects to the vehicle's Bluetooth, the "Do" is to "Open" the Amazon Music app. Unfortunately my car media player will only connect to the app if it is both "Open" and "Playing." I see there is an automation programming option to "Play" music if using the built-in iPhone 'Music Player,' but I can't figure out how to program the Amazon Music app to begin playing automatically. So presently, in order for me to get it working, I still need to pick up the phone and press the "play" button in the Amazon Music app every time I start the car. Thanks in advance for any assistance with this!