There are many situations that cause sleep grunting, which can be considered to be caused by the following reasons: First, it may be caused by dreaming, if you dream of some familiar scenes or scary and exciting scenes when you sleep, then these will stimulate the body to make a series of reactions, such as sleep grunting, and may be accompanied by some other small movements. Second, it may be caused by physical discomfort, such as sleeping on one side for too long, resulting in numbness in the arms or legs and feet.