I have experienced a few encounters with the phenomena, although I note my experiences were less frightening or alarming than they were enraging. Each time it has been the initial shock of being enfeebled, followed by a surge of fury which allowed me to break it. Similar to the notion of "moving your toes" although my reaction was to strain every inch of the body to resist and mentally motivate myself to fight free. Fortunately this resulted in the episodes being extremely brief, a few moments of tremendous trembling as everything works to break the paralysis, but never as disturbing as some have reported. I suppose that might be in part due to my reaction being one of intense, single minded will to escape and get free and or fight back against what initially feels like an attacker. The only downside being almost throwing myself free, but I suspect that would be a small price to pay to no longer feel disabled as that.
As for how the incursions upon sleep came to be, yes, odd sleeping behavior and positions were the issues I suspect, such as not sleeping in a regular format I am accustomed to. The oddity in it all was an overwhelming atmosphere of darkness, that the world felt darker, appeared darker, and gave a malevolent air to it. That too likely added to the fight and or flight response.
