S.B.
Tracy gave you excellent advice - definitely ditto to everything she said! My son is 3 and is shy. I didn't even really figure this out until more recently, because our life hadn't changed since he was a baby, so he already knew everyone...
The only other thing I would highly recommend that was recommended to me is to not label your son as shy. Don't even say the word. The label may help him "hide" better, and also whenn you label him to others, it also gives an outlet, both to him and the person trying to draw him out. The label allows a reason for not dealing with it. (If that makes sense.) It is better to say "he takes longer to warm up to new situations" and leave it at that.
I hadn't thought about it until someone gave me this advice, and I think it really works. I slip all the time and call him shy though when talking about it with friends (and the internet, haha) but in new situations, I now just say he needs to warm up.
Good luck with the move!