I have had similar jolts to the body and also out of nowhere. Would often happen in the semi-conscious time just before going to sleep, although no regular pattern to it.

I did however have a dream which caused a jolt through my body. I dreamt I was in an empty room looking towards one corner. To the side was a window, and coming through the window was enough moonlight to see the corner of the room at which I was staring. I could also sense something behind me but I couldn't turn to see, when suddenly something struck me across the back of the neck with such force that it caused me to physically jump out of bed and turn the light on to make sure there was nothing in the bedroom with me. Had me so freaked out that I kept the light on for the rest of the night.