He so shy!

My 4 year old son is getting ready to go to school next month and he is very excited. He went to school last year but only for a while so he knows what it is like. The only thing is that he is very shy and won’t ask for things sometimes. Last year he had a couple of potty accidents because he did not want to interrupt the teacher. He loves to play with the kids and gets along well with them but when they sing in the morning and things like that he is afraid to do it because he is so shy. I don’t know why but he also gets nervous, i am trying to teach him that there is nothing to be afraid of. I I know where he gets his shyness from , Me because i was a very shy kid an sometimes still am. I know that he might grow out of it but i want him to be able to participate in everything so when he goes to kindergarten he is used to it all. I know he might change but i just can’t help but worry about him.