I recommend powering off your phone, then powering it up and making sure you have the latest iOS updates and Spotify updates. My experience on Android with Spotify has been great.
I have had similar spotty issues with Spotify. So far about three different issues since I started using it but on three different occasions, not once per hour as mentioned. Each time I have had to disconnect and reconnect my iPhone and/or close/reopen app directly on the iPhone.
I don't think it's CarPlay as much as Spotify not working well with CarPlay. I have had similar issues with Tidal in the past without CarPlay, as it requires login like Spotify, which Apple iTunes/Music doesn't as far as the App itself.
I thought it was the USB in my car. All I ever run through the phone is Spotify (sounds much better than the Blu-tooth). It crashes CarPlay all the time. I haven't tried using a different music service to see if that fixes it.