Ahh, so glad I can answer this for people. After my first episode in 2003, I have had it sporadically. Usually it has come after some type of treatment (at first IV steroids, after that different supplements). Perhaps surprisingly, unplugging electronic equipment and putting my cellphone in a different room helps to decrease them a little while I sleep. So I think some of this is our bodies on super high alert. I got the type in the brain (see below) every time I used concentrated oxygen.
It is called 'hypnic jerking'. I cannot believe it too me so long (and took so much money) to figure out what they were. And still, there is a lot that is not known about them. Doctors say that research demonstrates that it does no damage to the brain. That is, other than wrecking sleep patterns if it gets bad. IF you have it along with a 'live dream', then it is called a 'hypnopopic or hypnogogic hallucination'.
An example of these hallucinations would be if you were dreaming of falling and then kicked your legs... or dreaming of pushing someone away or tapping someone on their back, and your hand or arm jerks. They are involuntary myoclonic twitches that are reportedly more muscular in origin than neurological. At least that is what this sleep specialist told me. I don't believe him 100% because he said that no one knows why they occur. When I asked if it could possibly be due to infection, he said no. WHA?????
He said the reason why we don't know more is because there is no money put to research it due to the fact that they are not dangerous and they occur with healthy individuals. However, in my case, they prevent me from entering deep sleep. My sleep has become so disturbed from it.
He said that the best treatment to date is nightly Ativan or Klonipin (or some other benzodiazepine). I take the former along with some supplementation (L-Theanine, sometimes L-triptophan, etc). I try not to get to the place where I was habituating (was at 8mg per night of Ativan).
Someone explained to me that the enzyme used to put the body into a paralyzed state during the night can be missing in my circumstance. I don't know what that is, I'd love to figure it out. I'd also love to figure out why if I don't jerk, I parch awake.
One website says that hypnic jerking that happens every 30 seconds is called Periodic Limb Movement Disorder. However, in my case, my jaw will move, sometimes (occasionally) my whole body, like you mentioned. The scariest for me has been what I call 'brain twitching'. The sleep specialist that I mention above said that it is deferred, that it is impossible that it is happening in my head. However, when I went home and did a search on it, low and behold, it came up.
The following is from:
Another theory put forward to try and explain the hypnic jerk is that the body reacts to falling asleep much in the way that a body may twitch when dying. The hypnic jerk is a reflex used to keep the body functioning. The brain might register falling asleep as a situation in which the body needs to be stimulated.
A hypnic jerk can also occur when you wake up. This is far more rare and can also affect auditory as well as muscular nerves. In the phenomenon known as an as auditory sleep start, waking from sleep is accompanied with a very loud snap or cracking which seems to come from the center of the head. Some people have also been known to have visual sleep starts, in which a blinding flash of light awakens the sleeper, but these cases are also extremely rare.
Sleep studies have shown that hypnic jerks affect around 10 percent of the population on a nightly basis. Almost 80 percent of people are affected occasionally and 10 percent are rarely ever affected.
Hypnagogic hallucinations are hallucinations which occur at the boundary between sleeping and waking. They can occur when people are falling asleep, or when they are starting to wake up, and they tend to be extremely vivid, feeling like a Technicolor Oz after the black and white Kansas of every day life. Many people experience hypnagogic hallucinations at some point during their lives, but recurrent intense hallucinations can be a sign of an underlying medical condition which may require treatment.
Visual, auditory, tactile, and kinetic sensations can all be experienced during hypnagogic hallucinations, and everyone experiences slightly different forms. Some people, for example, may feel like they are falling, and jerk themselves awake to avoid hitting the ground. Others may hear voices as they are trying to drift off to sleep, or experience a vivid sensation that someone or something is in the room. Sensory experiences such as feeling like one is submerged in a pool of water are also not uncommon.
In some cases, hypnagogic hallucinations can be frightening for the people who experience them. They may include vivid and frightening images, including images which are out of scale, which can make the hallucinations seem even more unsettling; people may see giant spiders on the walls, for example, or feel like they have shrunk down to a tiny size in the bed. The vivid experiences may also be brought to mind over the course of the day, causing inexplicable images or sensations to filter through someone's consciousness at an unexpected moment.