I should have blogged about my night terrors years ago! Stephanie just linked me to a treasure trove of information about sleep paralysis. Sleep paralysis! Of course!
According to this site:
Sleep paralysis is a condition in which someone, most often lying in a supine (face up) position, about to drop off to sleep, or just upon awaking from sleep realizes that s/he is unable to move, or speak, or cry out. This may last a few seconds or several moments, occasionally longer. People frequently report feeling a ‘presence’ that is often described as malevolent, threatening, or evil. An intense sense of dread and terror is very common. The presence is likely to be vaguely felt or sensed just out of sight but thought to be watching or monitoring, often with intense interest, sometimes standing by, or sitting on the bed. On some occasions, the presence may attack, strangling and exerting crushing pressure on the chest.
Thank you, Dr. Seery-Murphy. Many, many thanks!
The Outside Lane 
Well, for heaven’s sake. I KNEW my vast knowledge of trivia would come in handy someday! You are quite welcome.