It's definitely happened once at least for me, and I remember the sensation of being unable to move and the sensation of absolute terror. I remember that I thought/dreamed that there was a huge funnel of cobwebs surrounding me and I could not get out--believe me, it would've given that spider scene in
Chamber of Secrets a run for its money--or spiders, as the case may be. I'm amazed I didn't get PTSD from this sleep paralysis, which apparently can and has happened in the past.
What about the sensation of the earth moving or hearing something in your dreams that you know is not a good thing? I know whenever I dream there's a huge quake, I can often feel it as well, even though there isn't an earthquake in reality. However, there's no real sensation of terror around it, so I guess it wouldn't really come under sleep paralysis.