Old Hag Syndrome

An apparition reported to resemble an ugly woman with tangled hair, rotting teeth, a hooked nose, mad eyes and claw-like fingers. The Hag is also related to the mara (from which the word 'nightmare' is derived), a demon that likes to attack humans at night and abuse them.
Victims of hag attacks (known as Old Hag Syndrome) claim that they awake abruptly to find that they cannot move, even though they can see, hear, feel and smell. There is sometimes the felling of a great weight on the chest and the sense that there is a sinister or evil presence in the room. Old Hag Syndrome has been documented since ancient times and modern research suggests that around 15 percent of people experience at least one Old Hag attack in their lives. The name of the phenomenon comes from the superstitious belief that a witch - i.e. an old hag - sits or 'rides' the chest of the victims, rendering them immobile.
Sceptics argue that rather than witches or demons there is probably a medical or scientific explanation for Old Hag Syndrome, such as indigestion, sleep disorders or repressed tension. Some researchers believe that takes and encounters with the hag might be attached to the phenomenon known as sleep paralysis. Medical explanations, emotional tension and sleep paralysis can explain the great majority of cases, but not all.
Have any of you ever experienced this?
I have a couple of times in my life, but every time I have, I felt like I was in a state in between being asleep and being awake. I would try my hardest to move and wake up, but I couldnt. So I would try to talk and wake myself up, and still couldnt do that. You feel trapped inside you own body. Its actually quite frightening, but I have never thought it to be paranormal.