Remember your ABCs
Until your infant's first birthday, they should sleep alone, on their back, and in their crib for naptime and bedtime. We know that infants who sleep on their stomachs are at a much higher risk of dying than on their backs. Infants who are placed on their sides are more likely to roll over onto their stomachs, so side sleeping is not recommended.
Some parents worry that an infant on its back will choke, but the infant's airway anatomy and gag reflex will prevent that from happening. Even infants with gastroesophageal reflux (GER) should sleep on their backs. To see the position of a baby's airway while sleeping, watch this The Cribs for Kids® video.
Once your infant is able to roll from their back to their tummy and then roll to their back again, you do not need to reposition them. But always put them down to sleep on their back when they first go to bed.