My G lowers it’s idle while at a stop with the AC on it goes below 500RPM and shakes a little the comes back up to normal. Now I notice it started doing it with the AC off. Anyone know what this could possibly be from?

 

A common/known issue for some cars:

https://www.myg37.com/forums/engine-...n-drive-d.html

https://www.myg37.com/forums/engine-...-in-drive.html

A simple search.....