Sleeping position reflect personality, because while you are asleep your body movement will try to get you to the most comfort position without conscious. The same as personality, they are internal (The way you are, things you are feeling natural). Think about what hypnotism do.

According to google: * Fetal, on side with bent knees (41%) = Personality: tough on the outside, sensitive, shy and quick to relax * Log, on side (15%) = Personality: easy-going and sociable, trusting of strangers and gullible * Yearner (13%), on side with arms stretched out = Personality: open natured, slow to reach decisions, suspicious, cynical and reluctant to change * Solider, flat on back (8%) = Personality: quiet, reserved, set high standards for themselves and others and doesn’t like a fuss * Free faller (7%) on stomach with hands above their head= Personality: brash, thin-skinned, outward confidence and responds poorly to criticism * Starfish (5%) on back with arms above their head = Personality: a great friend, happiest out of spotlight, good listeners and has a willingness to help

Your sleeping position could also be affected if you have certain medical conditions.