I usually fall asleep to the side, left side up. In the middle of the night I sometimes switch to the other side or if it hurts I switch to sleeping on my stomach (with my face towards the side I should be facing if it didn't hurt). Closer to the end of the night I sometimes sleep on my back, since it makes it more likely for me to have lucid dreams.
I used to sleep only to the sides. A few years ago I started having some problem on the right side of my bowels which was likely to hurt if I slept with the right side up, and sometimes I wouldn't even be able to move or get out of bed. So to avoid always sleeping to the same side, I started getting used to sleeping on my back and on my stomach.
Pitch black dark, with the fan on, one arm under the wifes head/ pillow and the other around her belly, her facing away from me, with the Windows open most of the time. No pajamas, just boxers. Just a thin blanket.
Most of the time, I sleep on my side.Sometimes on my back, and occasionally I'll sleep on my stomach. This made my doc. to recommend a pillow from https://hovement.com/best-down-alternative-pillows/ with an aim of helping cure the recurrent pains. Trust me, within no time, all was well. With time, I've found myself start out on my back, but wake up multiple times during the night while flipping from one side to the other. There is a day I almost fell off the bed, hahaha.
I sleep in the fetal position with the obligatory thumb in my mouth, lol. It is the usual sleeping position but I'm the normal type of guy. It is the only normal thing I feel that I do sometimes, gosh, lol.