What is going on with my hermit crab?

i just got a hermit crab about a week ago. And every time i am around he is never out of his shell. He always buries himself in the sand. I just gave hime a bath yesterday but still nothing. I wake up in the morning and he has moved an inch it looks like he eats and drinks. I have tried to hold him and play with him but he never comes out...what is going on...???