Many stage actors and public speakers are shy. Yes, they are, but get them on a one to one (or a few) basis their shyness really shows.

Low-self esteem is the route of it.
CANDC (above post) pointed to accepting oneself as a means to overcome it. This is true.

I suffered very low-self esteem many years ago. I was so afraid of looking at people in the eyes for fear that they may see in me what I even didn't want to see in me.
I walked everywhere with my head down at the ground, only glancing up know and again to see where I was going.

To overcome this took me a few years of self-honesty and exposing my honesty to others. I still do today.
After I got over the initial fears of exposing my secrets to my therapist (much like a confessional) and realized that I was not that bad after all.
But most importantly, I realized I was not the only person with secrets - everybody has them.

Once I exposed my secrets, I no longer felt ashamed and fearful about myself. I accepted who I was.
Over time, I could laugh at myself in the company of others. I can freely talk about some of my crazy thoughts of the past and laugh at them.
The real funny thing is, all my friends can relate to them.

Self acceptance not only builds up our self-esteem, but can get to a point where self-esteem is no longer a need as it used to be.
A person no longer feels threatened about who knows who they really are.

No more shyness!
No more fear of what others may think of me, because I know my truth. If others think of things that are false about me, then that is their problem and not mine.