Audio dropout with usb connection in car

I have an iPhone X and whenever I try to play music in my car using a USB cable, there is frequent audio drop out. This happens regardless of the type of cable including brand new Apple USB charging cables. This does not happen if I play music via Bluetooth. As part of trouble shooting recommended by Apple, I have reset all the various kinds of settings and have even restored the phone as 'new' without backing up to a previous backup. Of note, there seems to be a difference quite often in that I notice the breakup more during daytime hours, but when driving home late afternoon or in the evening hours, it happens far less, or not at all. Despite restoring etc, I wonder if it is possible any of the apps can be interfering with audio playback when connected via the USB cable. I get the same thing if I try using the Amazon music app or a YouTube video. I would hope someone can offer some suggestions. The phone is updated to the most recent iOS 11.2.6. I also wonder if it can be a hardware (phone) issue.