Has anyone here experienced a 'dream within their dreams' before?

What I mean is that, while dreaming, you slip into another dream without warning - only this dream is real, and you have no idea that it is until you 'wake up'. Unlike a normal dream, there is no control in this second dream. Your body acts entirely against your will, and you might very well walk into a dangerous situation without knowing better. While it's happening, however, everything makes sense to you.

If this has happened to anyone else, please share your experiences with me. I want to know how common this is, and if there is a way to fight it somehow.