Positions vary from person to person, but there are essentially only three basic patterns - the rest are modifications of the same patterns. Each one has its very own set of challenges which we'll highlight. The focus for the mechanical piece is to create a pattern that promotes deep sleep for an optimal period.
Although you may not stay in the position all night, the fact that you've begun your sleep in optimal position will improve the quality of time your in a regeneration cycle.

Front lying - (The Log) 14% of kiwis sleep in this position. The risks associated with this pattern are mechanical; accentuated back arch, end range neck rotation including an extended neck position when lying on a raised pillow. To improve this position use a flat pillow for your head and another pillow or rolled up towel under your belly button.

Back lying - (Starfish) 28% of kiwis sleep in this position. The risks associated with this position are breathing obstruction and or sleep apnea. If you are overweight, the weight pressurises your abdominal cavity, and pushes your chin down, closing your airways and challenging your autonomic breathing ability. Avoid this position where possible.

Side-lying - (Fetal) 58% of kiwis sleep on their side. This by far is the most optimal variation for sleep. It supports a neutral position across the entire spine. To improve this position try putting a rolled up towel into the front of your pillowcase to provide better neck support and place another one between your legs or cushion under your knee if bring your leg across your body.
The most powerful neurological position to live in and sleep in is Side-lyingNeutral. The further you digress away from this position, the greater the neural load and the less brain body connection can be supported, reducing the effectiveness of the sleep. What’s worse is that you are promoting a physiological environment for sleep disturbance and or sleep apnea.