Some signs that a person abnormally jerks his body during sleep include injuries, discomfort and poor-quality sleep, notes The Sleep Center. These sleep starts or hypnic jerks can also cause symptoms during the day.
The condition of jerking while sleeping is called myoclonus, according to the National Institute of Neurological Disorders and Stroke. It is caused by sudden muscle contractions or relaxation. The person cannot control these jerks, and the jerks can happen infrequently or as often as every minute.
Myoclonus can be a sign of several other neurological disorders, such as Parkinson’s disease, Alzheimer’s, multiple sclerosis and epilepsy, notes the American Sleep Association. Myoclonus can also precede more serious conditions, such as restless leg syndrome and periodic leg movement during sleep.