He is being submissive and his confidence is low. It will improve as he gets older, but he needs encouragement and praise to help build his confidence.
Don't scold him when he does this as it will only get worse.
Call him and have him come to you instead of walking over to him and towering over him.
Bear, Anna, Molly, Ossie, and The Countess Lisl von Schlaf
An Unhappy German is a Sour Kraut!