Idle animation for custom mob?

Hi,

I created custom mob in BlockBench and expoted it as Java entity, imported to MCreator..

In the java file of the mob that MCreator creates i can add custom animation for the, lets say, tail of my custom mob, i just need simple MathHelper.cos, same as legs and arms.. but that animation is only applied when mob starts walking..

How about the idle animation?  Is there a way to add tail animation when the mob is idle?

Thanks