Thanks for reaching out Steelmag6,
it sounds like you're having trouble with playing Apple Music over your car stereo using a wired connection. It wasn't clear if you are using a USB or 3.5mm AUX connection, but these steps on How to connect your iPhone, iPad, or iPod touch to your car can work for both:
Connect using USB playback
1. Restart your device and your car.
2. Make sure that your device is unlocked and on the Home screen.
3. If possible, try to connect using another cable or USB port. Check the manual that came with your car to learn how to connect an Apple device.
4. Check your charging port for any debris or damage. Make sure that your charging cable is properly inserted into the port.
5. Update your device.
6. Make sure that your stereo is using the latest firmware from the car manufacturer. Check your car's manual for more information.
7. Try playing audio from a different app. If you can't play audio from a third-party app, contact the app developer for help. If you can't play audio from an Apple app, contact Apple Support.
Hope that helps.
Take care.