I understand that you're having some issues pairing your iPhone X with your car stereo. I'm happy to provide some help for this issue.
Check out the following article for help with this issue:
Get help connecting your iPhone, iPad, or iPod touch with your car stereo - Apple Support
If you're using CarPlay, the following article can also help:
Set up CarPlay with your iPhone - Apple Support
If CarPlay doesn't work like you expect, here’s what you can check. After each step, try using CarPlay again.
- Make sure that Siri is turned on.
- Restart your iPhone and your car. Depending on your car, you might see the CarPlay Home screen when you turn it on. If you don't, look for the CarPlay logo on your car’s display.
- If possible, connect your iPhone to a different USB port in your car.
- Try a different Lightning to USB cable. Make sure that the cable is certified.
- Update to the latest version of iOS.
- Check your car’s manual for help. You might need to install firmware updates for your stereo.
Thanks for using the Apple Support Communities. Cheers!