The child is asleep, but why do their hands and feet always move every 2 to 3 minutes, and why do they make noises in their mouth?

Patient's question:

The baby is just 20 days old. Why does he always stretch his hands and feet every 2 to 3 minutes while sleeping and make "Hmm" sounds? Is this normal?
Is it normal to feed him when he's asleep?
Sometimes he vomits milk while eating.
He is fed with a bottle.

Doctor's answer:

It is a normal phenomenon, no need to worry too much.