In '12 Rules for Life,' Jordan Peterson states that the two most primal human fears are:
the fear of death and
the fear of social judgement/humiliation.
Is it any wonder we run away from public speaking?
The bad news is if we give in to the fear we're admitting to ourselves that the speaking opportunity is too much for us to handle, thus making it even less likely that we will accept such opportunities in future.
The good news is, if we choose to pursue the speaking opportunity, the grizzly bear of fear will seem ever so slightly less scary next time.