Found an interesting link that seems to describe it appropriately:
http://serendip.brynmawr.edu/exchange/node/1740
Hope it helps.
I believe it has something to do with the mind's eye, so to speak.
Try this when you've just woken up in the morning and you have the day off:
Wake up, make sure you're still rather sleepy.
You will be able to fall back asleep rather quickly, we will use this.
Stay in bed, close your eyes, and try to fall back asleep.
When you're about to lose consciousness, think of that feeling; actually, try to feel that same feeling.
If you are experiencing what I believe it is, the feeling will grow until you will find yourself in a state of semi-consciousness where you will have your eyes open, in your room, as if you were awake, but your mind will be feeling these sensations. I must warn you, however, that there may be sounds and things/people that may be present. These exist solely to scare you, so I've been told. Also, doing this too often may result in you automatically thinking this before falling asleep, and you may get it repeatedly.
Personally, I feel a strong tingling sensation all over my body and my ears block, as if they were under pressure.
I have this too when im laying down in bed resting or trying to go to sleep i have had it sitting down as well...some times thoughthey are very strong..like a violent earthquake and i get scared cuz im not too sure if it is an earthquake or not...now im notcing more often than not it is me, it happens every night i think....it bugs me sooooooooooooooooooo bad its very annoying it feel like my bed is shaking..i dont want to go to the doctors though becuase i think they will just chalk it up to my bi polar disorder diagnosis..which thats what they told me last time and tried to give me meds...or they will just not find anything wrong at all..but now i clearly see i am not the only one who experiances these wierd things....im more annoyed than concerned
I asked this question on another forum and someone mentioned that their doctor told them it was orthostatic blood pressure but you can't take that as a personal opinion since it can be totally something different. at least we know we aren't the only ones! we also said she noticed it while sitting down sometimes too and I think I also have felt a "earthquake" sensation while sitting at times.
i get this feeling as well, and sometimes it is what wakes me up at night, so i usually go and get a drink of water and go back to bed. But yes you are not alone with that one, its odd though i would like to know what is doing/causing for this sensation
it's also not the feeling where i'm about to fall down so i wake up suddenly.