When i was a kid i was sleeping on my stomach and i’d have my hands on each thigh, arms tucked in, so the weight of my torso was more on my arms than my thorax for better breathing.

But then i grew down there and that got uncomfortable, so i bent one knee for the room and the hand can’t be tucked on my thighs. So now i bend each arm and put them under the pillow, also shifting my weight on the one opposing my bent knee.

That’s kind of a in between stomach and side but of course letter on i also adopted the side position to switch to, mostly because of my back getting old.