I can't understand how anyone can sleep on their back. They snore and can't breathe it's like they're dying it's pretty obviously wrong.
But I’m also very much in shape with no excess weight, snoring is generally correlated with ill health and being overweight.
Also, my previous cats preferred to sleep on my chest, so they trained me to sleep without a lot of motion. Currenrly, one cat likes to sleep on my legs and overheats them, resulting in a lot of movement at night; the other cat will only briefly visit at night, but will help me stay in place for naps on the couch.