
Have you had his eyes tested? One of my girls is partially sighted as her lenses never developed at birth. She is not nervous but doesn't like people coming up to her and touching and takes a while to get used to dogs and people that she doesn't know.
We never realised until she had her general eye test that there was anything wrong, although did wonder how a dog that looked extremely confident when she walked into a room wouldn't allow everyone to touch her. Now I tell people not to bend over her and touch her. If people listen to me she is all over them after about 20 minutes as she has gone up to them not the other way around.