CarPlay connection turns my car radio off

Every time I get in my car and my phone connects to CarPlay, it turns off the car radio (ie the radio station I was listening to stops playing - the car media screen is still on). There's no media playing on my phone.

How can I get CarPlay to connect (so I can use my phone's maps), but leave the car's radio playing?

I can just switch back to the car's menu and turn the radio back on, but I don't want the radio to be turned off in the first place.

Any ideas?

I found something that said I can use an automation to do this (along the lines of: when the phone connects to CarPlay, pause media on the phone), but this doesn't work for me.

Thanks