Hi there
Please try this
Download a test track: Open the Apple Music app and download at least one song or audio file back onto your iPhone 13.
Use an alternative streaming app: If you are trying to play Spotify, Podcasts, or YouTube Music, make sure the app is actively open and playing audio on your phone speaker before plugging the cable into the car.
Toggling the EQ: Go to Settings > Music > EQ and turn it off or cycle the setting, which forces the internal audio handler to reset.
Restart and reconnect: Force restart your iPhone 13, turn off the car ignition, and plug the USB cable back in once both systems reboot