Hi Fallen T.
If you research the phases of sleep that most go through normally you come across the study of how close your brain reads to an awake state during REM or Dream stage. the fact that you are waking in this stage is common. Dreams are so vivid and powerful, they span all of our experiences and go way beyond. Our Brain constructs millions of bits of information and processes it in the dream realm. Emotions that are generated through out our consious life is reconstructed in our dreams though the situation and interpitation of these things may be as simple as remembering the emotion of a taste of a certian food but in the dream construction it plays out as an epic story of adventure and comes so close to matching or excedeing the waking state that you actually phase to an imediate waking state feeling all the intense feeling of the construction that your brain was playing out.
Have you experienced an inability to move when this happens?
This is called Sleep paralysis. evreyone is suppose to have this happen when they enter the dream stage of sleep. some times we experience this on the onset of going to sleep and are awake when it happens. and when we wake up. It is normal to experience this on occasion but if it is happening frequently and even through the time of the day when you are awake; you may have a serious problem, Myself, I have a sleep disorder that has all the REM problems along with Cataplexy and EDS and HHalucinations (dream intrusions while being awake), Sleep paralysis, all of the markers for Narcolepsy. I have dealt with this diagnosis for more than 25 years now and have recently (2009) had the Diagnosis re evaluated and have confirmed it with modern sleep study and multisleep latency tests I also have both kinds of sleep apnea (obstructive and Central)
I find the subject of sleep and how it affects our lives to be very interesting and extensive topic to research. I hope this little tid bit into the realm that I spend most , has helped. Oh, one more thing, recently it has been discovered that REM isn't the only phase inwhich people dream,,,there are deeper phases of sleep that we dream in but the brain wave patterns seem to imply that these dreams are very much different that what we experience during REM. New discoveries are being found every day. thanks for letting me share.