Does Android Auto open automatically?

Currently, the Android Auto app automatically launches itself if you connect your phone to a car and unlock your phone (presuming you have the app already installed on your phone and that you have a head unit that supports Android Auto).

Why is Android Auto not working?

Clear the Android phone cache and then clear the app cache. Temporary files can collect and can interfere with your Android Auto app. The best way to ensure this isn’t a problem is to clear the app’s cache. To do that, go to Settings > Apps > Android Auto > Storage > Clear Cache.