I have my 16 inch ball in a 20 gallon. Also, make sure your temp and humidity is correct because I've read in a few different places that snakes sometimes move around to try and escape too-hot temperatures.

But, I don't think that's the case here. Just like everyone else said, I think he's just acclimating. Definitely don't feed him yet. He needs to get comfortable with his new habitat. Also, when you do feed him (if you decide to feed him outside of his regular enclosure) make sure to wait 30-40 minutes before placing him back into his normal habitat. This allows for him to digest a little so he won't regurgitate when you handle him. Make sure to place him back in his cage very lightly so you don't upset his stomach and try not to hold him where the mouse is sitting inside of him.

That's a long post. Sorry