Night Paralysis

I have suffered this condition for many years although not so often in recent years.
It is frightening, and I've often thought that while trying to wake up completely I'd suffer a heart attack. Researchers do not understand what is happening but I do know that it happens in countries across the globe, where people often associate it with a 'devil' sitting on the person.

What happens?
I wake up, normally during a dream, but although I am aware, I cannot move as I'd wish. In my case the condition persists for some time, causing panic to set in. I become more and more desperate to move a leg or arm say, putting enormous amounts of stress into the effort. It is at this time when I think I could induce a cardiac arrest as failure to make the muscles respond increases the panic and stress. I can think clearly about trying to relax but its almost impossible to lie there dormant while constricted.
I don't know if I'm lucky but I don't suffer from total paralysis. I can make some grunting noise, and make minimal use of my finger tips or toes to alert my wife who now recognises my condition. She wakes up and vigorously shakes me until I fully wake up, a process that can take some time and effort.

What is it?
I can believe it's a stress related condition, probably most common during ones middle years. I can't remember suffering as a youngster and now that I've retired I've had only one attack this year.
That doctors cannot find the cause should be no surprise, particularly as it seems to be associated with REM activity and dreams.
It is my opinion that dreams are a fuction of brain activity subject to actions and reactions involving the function 'i' or the square root of minus one. It is impossible for our brains, as currently constituted, to understand this function, but the workings of the brain use it. In the future, evolutionary development of the brain will enable us to fully 'see' this dimension.