Hi! I am kind of a shy person, depending on my surroundings. But for work it’s different. I always liked being on plays in school, organizing shootings and all so for me it was just exciting, but being focused and comfortable definitely takes time. I definitely felt awkward a gazillion of times, or woke up completely OFF many days, I still do. When you can sense so many eyes on you, it’s easy to get self-conscious, so the biggest thing is to be AWARE of yourself the whole time. Of your body, of your self and the space you’re at. Not so much on what people are thinking. I’ve been to castings where you have to cast in front of all the other models, and the times when I cared about their opinion or approval were the ones where my performance was the poorest. 
One way of overcoming it…I think breathing helps you calming down. Think of the space in your belly, place one hand over and breath in and out a few times. When you’re “at home”, you will feel more present, confident and relaxed!