I read this.
This is common. Your little guy needs confidence.
Part of his fear is the unknown. His inexperience means he can't be confidence. His lack of confidence means he's terrified of the unkown. Definitely keep him on the leash and walk him outside, even if you only get 3 feet each time. Work up to the block. Patience is key, and it may be a week or so before you see improvment.
Use treats to reward him, but don't coddle him or pick him up if he's scared. This only translates to him thinking there's justification for his fear. Stay near him and let him hide by you if he feels the need, but no baby talking or high pitched voices, just soothing praise and treats.
Other basic things that help boost confidence: a strict schedule every day helps since dogs thrive on predictability and socialization with other dogs helps a LOT since they "teach" each other the ropes. Basic obedience training also bonds your dog to you and learning really builds self confidence in dogs.
Makes sense to me.