For those who are
having weird and very scary night experiences, I think much of it can be explained as the start of an out of body experience - where your 'astral body' separates from your physical body.
This forum
(astralpulse.com) is one at which loads of people who do out-of-body-travel (OBE) post. They give some of the signs (link below) they get when starting to separate from their body and many are what we here would describe as weird and scary. Things like feeling creatures on your bed, total inability to move, people/ghosts near to your bed, general night terror-like things.
Now, it seems to me that if these OBE guys are describing the kind of things everyone else is attributing to night terrors, paralysis, etc, then it is pretty much likely that these are the same things and they are a prelude to these out of body experiences. There are enough on there who claim they can do it to make it probable this is what everyone is experiencing, but just not getting out of body into the astral because of fear.
So,
here is a thread giving a whole list of things people have experienced. They include really loud and real earthquake experience (but nothing physical moves), as well as bangs, gunshots, whistling, music, buzzing, as well as pushing on the underneath of the mattress too.
There are many good threads, ebooks, and book recommendations in that forum as well.
Hope this helps some people who are having these kind of experiences and goes some way to explaining what is happening to them.
Also,
this website for more information (astralvoyage.com) too
Even if you dont believe there is such a thing as out of body travel, at least you need to look for the possible explanations if you are having strange nighttime scary episodes.