It might seem like your dog would be more comfortable sprawled out on the couch than curled up in a little ball in the corner—and he probably would be! But some dogs sleep curled up nonetheless. Why? Blame evolution!
Dogs in the wild will dig a nest to sleep in, and curl up in it—especially if it’s chilly. This will help keep them warm and also keep their most vital organs tucked away from predators. So there are two good reasons why dogs developed this behavior. If your dog stretches out when he sleeps, he’s either really hot or he feels safe and secure.
You might want to get your dog a small, round dog bed that he fits in, which will make him feel cozier. Or you could give him a blanket and let him "dig" his own little nest.