Mines the same! We've decide to do 2days a week with a childminder.... (starting tomorrow) smaller group of kid around his age, so hopefully it will bring him out of his shell. I'm not overly worried with him around adults (stranger danger and all)
My eldest daughter is the same. She is now 10 and coming out of her shell more every day! Some kids are just super shy, I was when I was a child.
My little boy the same! Even if In the shops or just out he will bury his head on the floor until I pick him up x
Maybe attending a couple of groups with him to get him used to being around different people (especially before starting nursery)
My daughter is the exact same, i ent overly worried! I just think she will come out of her shell evenchally x