Hello there laVelle1952,
Thanks for posting here on the Apple Support Communities! This is a place where other Apple users can submit questions or respond to others to help lend a hand. Let's take a closer look as we do our best to provide some additional insight.
Since this only seems to happen while your phone is connected to your car, then that means your iPhone is likely trying to use an audio input or mic in you car.
Does your vehicle support Apple CarPlay? If so, you can try these general troubleshooting steps: If you need help with CarPlay
If your car does not use CarPlay, you may need to check the user manual or documentation that came with it to see how you can change or disable any mic/audio inputs that are built in to your car.
We hope this helps get you pointed in the right direction.
Take care.