If you look up hypnic jerk, though, it seems to be associated with people waking up in the middle of the night with some muscle movement, often accompanied by falling dreams.
This bed shaking, though, happens when we are awake and also is not accompanied (at least for me) by any kind of falling "dream" or hallucination. My muscles in my legs are completely still when the bed shakes. (I used to think it was my leg twitching so I paid close attention to this.) Also, I do think I have hypnic jerk from time to time, so I can see the obvious differences. This morning, for instance, I dreamed I was about to trip down some stairs and I woke up as my I was trying to catch myself, all out of breath. Or maybe hypnic jerk is as simple as your muscles twitching as you fall asleep, which also happens to me often. In any case, I definitely don't think it's related to the bed shaking.
Also, I want to say once or twice it did feel like someone was sitting on my bed or there was weight on my legs. It's a very creepy sensation. Although I'm not sure I believe in ghosts or spirits, I had a creepy feeling around that room because the door would also close by itself and at times it sounded like someone was playing with my toys as I was sleeping. I've experienced this problem at my mom's house, dad's house, and on my futon, so I'm more likely inclined to believe it it something about me rather than the beds I sleep on. I've never had it happen when I sleep next to someone, so for awhile I thought it might be in my head. I'm glad to know I'm not the only one.