TL;DR

This is mainly caused because Android Auto is designed with Google's native apps in mind. You can avoid this issue by disabling Android Autio notifications under the Google Messages app.

How to fix it?

You can easily solve this by disabling Android Auto from the SMS - Android Settings.

• Find the Settings App in your app drawer
• Go to Apps → See all ### apps → Android Auto
• Click Permissions
• Tap SMS
• Change the option to Don't allow.