Перевод (не очень удачный):
Hypnagogic Jerk: http://www.sleep.com/wordpress1/sample-page/sleep-disorders/hypnic-jerk/
More is below.
Ниже есть продолжение.
A...hypnagogic jerk [or hypnic jerk]...is a completely normal experience often described as a falling sensation or electric shock that occurs as we are falling asleep...These jerks are more common in people who sleep uncomfortably or are over tired. There is also evidence that the changes in body temperature, breathing and muscle relaxation that occur as we drift into sleep may cause the brain to misinterpret these as a sign of falling, signaling the limbs to wake up...hypnic jerk treatment is not required, as the condition is considered harmless. Good sleep hygiene comprised of adequate quality and quantity of sleep may however reduce the incidence of hypnagogic jerks.http://www.sleep.com/wordpress1/sample-page/sleep-disorders/hypnic-jerk/