The experience with Apple’s CarPlay was designed from the very beginning to be as straightforward as possible, so when you plug in an iPhone, the car automatically detects it and launches the dedicated UI on the HUD.

The default view is actually a CarPlay-optimized iPhone home screen that includes apps which make sense behind the wheel, such as navigation, and music playback apps.
And while Apple does allow users to configure what apps they want to see in the CarPlay interface, many just stick with the basics, and these include the navigation app of their choice (Apple Maps, Google Maps, or Waze) and a music app like Spotify, Deezer, or Apple Music.
But what Apple doesn’t clearly say is that you can automate CarPlay so that the experience is even more straightforward. For example, CarPlay can automatically launch an app like Spotify every time you connect the iPhone to the vehicle, all without you tapping the app’s icon manually.
Doing this doesn’t take more than a few seconds and comes down to an automation script configured in Shortcuts.
Pre-loaded on all iPhones running iOS 13, Shortcuts allows you to create automations for a wide variety of activities and apps, including CarPlay.
So before anything else, just launch Shortcuts on your iPhone and look for the Automation icon in the bar at the bottom of the screen. Next, tap the “Create Personal Automation” and then in the “Travel” section, tap “CarPlay”. On the next screen called “New Automation” choose the “Connects” option and hit the “Next” button in the top right corner.
You are now able to configure actions that will run when CarPlay connects, so tap “Add Action” and then the “Scripting” icon in the first row. Choose the “Open App” option in the “Apps” section – this should take you to the “Actions” screen, so just tap “Choose” and then pick one of the apps installed on your iPhone that you want to run when CarPlay launches.
Click “Next,” then “Done” and that’s pretty much it. Make sure you save this automation and the next time you connect the iPhone to the car Spotify should fire up all by itself. As a TL; DR, here is a summary of all steps:
Shortcuts > Create Personal Automation > CarPlay > Connects > Add Action > Scripting > Open App > Choose > Spotify > Next > Done

Apple has recently released iOS 13.6 with a bunch of improvements, and while users are generally recommended to update to the latest versions because of security reasons, drivers who rely on CarPlay for music and navigation would better think twice before doing this.

And it’s because this particular iOS update seems to be causing some issues with music players in CarPlay, and these include both Apple Music and Spotify.
First and foremost, it’s the “For You” tab in Apple Music that no longer works correctly.
As several users are reporting on reddit, enabling this tab and then tapping any generated playlist is no longer possible, as all they get is a loading indicator with no music actually starting playing.
The same bug has been confirmed by lots of users on various iPhone models, including both older and newer devices. The latest-generation iPhone is also affected by the problem, so it’s pretty clear that this isn’t a model-specific bug, but something that needs to be fixed in the operating system.
And then, there’s a similar glitch in Deezer and Spotify. After updating to iOS 13.6, I noticed that using the “flow” feature, which uses the songs I recently liked to generate a playlist that also includes other recommendations, no longer works. Once again, all I get is a loading indicator with no music actually playing after I tap the button.
This happens more often in Deezer, but I also encountered the very same problem in Spotify. However, I’m seeing isolated reports about the whole thing experienced by others with these players, so right now, the Apple Music bug appears to be a little bit more widespread for the time being.
I can't confirm all these issues are related, but it's pretty clear that the latest iOS version doesn't necessarily provide the best music listening experience on CarPlay.
Apple is yet to acknowledge these problems, but there’s a chance a fix would be part of the next update for iOS. Right now, it looks like a similar issue is included in the most recent version of iOS 14 beta too.