Ahhh....How old is he? My Roxy was like that when she was young. They all just have different personalties
I got Roxy at 6 months old. She has increased her outwardness about every 6 months. When I notice the changes in her, it makes me so happy! She is now 3 years old and she is still amazing me
I had gotten a couple of books when she was younger hoping to help her. I can't remember them all, but one was Help for Your Shy Dog. Maybe look into some books to teach you to help him

Some things they say is to build up their confidence - an easy way to do that is to teach them tricks or commands