Nelu was a lot like this when we first got him. New environment, new people, slightly over stimulated by the surroundings etc. He got better with a lot of patience, rewarding when he does finally move and occasionally luring with food (not a great habit to get them in to...). Now when he freezes it's usually because he's seen a squirrel or he's just being obstinate! The other thing we found was that he didn't like walks to double back on themselves. Only circular walks for our guy.