How do I stop android auto taking over my radio every 30 secs?

Open Android Auto Settings on your phone and choose to alter one or more of the following settings:

Start Android Auto automatically

Start Android Auto while locked

Start music automatically

There are many more settings that may be of interest.

13 hours ago, Mike495 said:

How do I stop android auto taking over my radio every 30 secs?

Maybe explain exactly what you mean by that, as AA has never done anything I wasn't expecting, and I can't think what you mean by 'taking over your radio'.