I sleep on my left side, angled, propped up with pillows. I use around 5 regular sized pillows with smaller ones. Sleep the best that way. I used to sleep on my right side but as I've gotten older, I switched, literal sides.
I sleep on my back, I used to sleep on my side, but surgeries to my kidney and nerve damage to that same side made it too uncomfortable, so I adapted to sleeping on my back.
Looks like we have a bunch of side sleepers! Sometimes I nap while on my side but I do find myself switching to my other side or just laying flat on my back. I think it has something to do with keeping a proper blood circulation.
I ask because I don't think I could share a bed, my family is known to be wild sleepers, my grandparents slept in different beds and so did my parents.