Because their spine is much more flexible than ours, cats can easily twist and turn themselves into pretzel-like positions without discomfort. Like us, cats can also sleep with their eyes open to some degree. The breathing fast and immediately laying back down does concern me a little, but it could be nothing at all. Don't panic, just wait till a vet is open, ask for an evaluation, and be sure to keep him warm and comfortable until then. I am, however, fairly certain he is just dreaming in his sleep. I have a cat with a large protein lump beneath his neck that causes him to wheeze in his sleep. The vet said not to worry because it wasn't malignant. I am hopeful this is the case for your cat as well.