Don't freak out just yet. A lot of clowns have some really unusual behavior. My clown sleeps at the bottom of the tank on his side. Several times I've thought he was dead. But, morning rolls around, and he's just fine.
What are your params? If they are okay, I would leave him alone to get used to things. If you start moving him around or mucking around with the tank, you're going to stress him out more.