Why does my young budgie wobble when he's on his perch?

I have a four month old budgie. He seems to be happy. He's a little quiet, but eats and flies fine. He's very tame and was hand -reared. Sometimes he just sleeps on my bed or a shelf or the bottom of his cage. Whenever he's on his perch (or similar) he wobbles, even while asleep. Can this be normal for a young budgie?