Lying on the side is the most common sleep position for humans. Interestingly, it’s also the most common sleep position for animals in the wild. Fascinating new research from Stony Brook University may explain why: A side-sleeping position seems to improve waste clearance from the brain, which could prevent Alzheimer’s disease and neurodegenerative diseases. >>> https://www.yahoo.com/health/the-best-sl...37202.html
Prophet Muhammad (salallAllaahu alaihi wasallam) used to sleep on his right side, putting his right hand under his right cheek, and this is what he recommended others to do. According to a saheeh hadeeth narrated from al-Baraa’ ibn ‘Aazib, the Prophet (salallAllaahu alaihi wasallam) said: “When you go to bed, do wudoo’ (ablutions) as if for prayer, then lie down on your right side…”
The Sunnah is to put one’s right hand under one’s cheek. It was narrated that Hudhayfah said, “When the Prophet (salallAllaahu alaihi wasallam) went to bed at night, he would put his hand under his cheek, then say, ‘Allaahumma bismika amootu wa ahyaa (O Allaah, in Your name I die and I live).’ Then when he woke up he would say, ‘Al-hamdu Lillaah alladhi ahyaanaa ba’da ma amaatanaa wa ilayhi al-nushoor (Praise be to Allaah who has brought us back to life after causing us to die, and to Him is the resurrection).’
Ibn Hajar said: The right side is singled out for a number of reasons, such as: this lets a person wake up more quickly; it also allows the heart to lean towards the right hand side. Ibn al-Jawzi said: the doctors have stated that this position is more beneficial to the body. They said to start by lying on the right for a while, then turn over to the left, because the former aids peristalsis and sleeping on one’s left side facilitates digestion.