Music always starts automatically on the same song when plugged in via USB/Bluetooth in car.

Hello Jim Jarvie,

Thanks for posting in the Apple Support Communities.

We understand you use your iPhone with Bluetooth and USB with your car stereo autoplaying music, right?

While your stereo doesn't have CarPlay features, the stereo manufacturer may still recognize the iPhone as an audio device to start auto-playing the music. We'd recommend confirming with the manufacturer if this is what's occurring, as well as if there is a setting to adjust this from occurring.

As for the same song playing each time, this is likely the first song in the list of songs in your library. If you'd like to try setting up a list of songs to play through, you can do so using the following steps. While this may not prevent the same song from playing as it's the first option in the list, it's worth a try: Add music to your queue to play next on your iPhone, iPad, iPod touch, or Android device - Apple Support

Choose what you want to play next

1. Open the Apple Music app and play music.

2. Find a song, album, or playlist that you want to play next.

3. When you find something, touch and hold it, then choose when you want it to play:

• To play your selection right after the song that’s playing, tap Play Next .

• To move your selection to the bottom of your music queue, tap Play Last .

We hope that's able to help understand what's occurring here.

Have a great day!