Hi. I used to be very concerned about my eldest child - at 3 he was shy, would completely freeze in new situations, simply wouldn't talk to people he didn't know etc. He was chatty and very articulate with me.
He refused point blank to join in any "clubs" until he was 6 years old. Even getting him to swimming lessons involved tears, meltdowns etc.
At nursery, he was happy to play, but refused to join in any of the activities involving outside teachers (private day nursery, so French, yoga, music groups etc).
Eventually, I just took a step right back, and just decided this was who he was, and stopped worrying.
Move forward 3 years - he is now in year 3 at his local state school. He is Class Rep, has at least 2 clubs a day, is confident in class, plays tennis for his club, football, swims, and has recently done his piano prep test - which involved going into a room, on his own, talking to and then playing to a complete, and pretty strict, stranger.
He is never going to be outgoing, and is still quite self-conscious, but it just shows you that they all find their own way, if you let them.