The nervousness before going in front of an audience is natural, and inherited from our ancestors. This brings to mind two points:
1. You can learn to move past it by understanding that the fear is probably overblown in your head. Truly, your mind is in fight or flight mode to protect you from dying, when embarrassment is the worst actual outcome.
2. When you don’t feel at all nervous, it may be an indication that you don’t care at all what the audience thinks, that is why your brain isn’t being triggered, there is no potential harm. As a trainer, I know that is the day I need to find something else to do for a living.