Being "sprawled out" means that you're laying down with your arms and legs stretched out wide. It looks like your body is in an "X" shape.

People can "sprawl out" on the floor, on a couch, on a bed, etc.:

A: Last night you were sprawled out all over my side of the bed.

B: Oh yeah?

A: I tried to roll you over, but you wouldn't move.

B: Sorry!