This used to happen to me when I was drinking a whole lot and on so many pills.
When it was time to wake up in the morning, my dreams would turn real but there was a sick feeling behind it and my actual body felt like moving since I thought what was going on was real but, I couldn't actually move, I just continued dreaming.
It was a sick scary nightmarish feeling, it was just like I was doing my normal day to day activity I would do in the morning. Walking out to my car to go to work, throwing out garbage on the way to my car in the morning. I saw and felt like the exact same environment, the daylight, how I normally walk, clothes I'm wearing, people walking past, the location of where I park my car... It was surreal. I can still see that image during one of those times. Cell phone ringing, people knocking on doors. I was really convinced that it was actually going on. There was no way to differentiate if was a dream or reality.
Then out of nowhere I would hear some kind of loud knock on a door or I would try to move my arm or leg with all my energy and suddenly snap out of it. Then I wouldn't really think anything of it, and think I was out of it, alarm clock hadn't gone off so I'd just ignore it, then I would just snap back into it repeatedly and all the dreams/situations were different making each "dream" seem that much more real. Since, I thought I had a bad dream, I woke up (from my sudden movements or those knocks on the door) but, I snapped back into that nightmare that seemed real but, in another situation.
I think this is what a nightmare would be but, it wasn't really a nightmare in the sense I was dying or getting killed or any danger going on but, it's just due to how realistic it was and so surreal, the timing, in the morning as I was about to wake up and I was going to do what I normally do in my day to day morning life, my exact same morning routine, but, my physical body felt like it was paralyzed and was just stuck since in reality I was really sleeping. One of the dreams that I recall was a time-frame was down to me leaving for work in the morning. These dreams or nightmares were what I would be about to be doing in reality if I had actually woken up.
In other words you could say, you were seeing yourself in the future 10 min. from the state you're in now. So, if you were sleeping about to wake up in the morning, I would see myself 10 min. in the future doing what I would normally be doing but, in reality I was still sleeping.
Usually based on how long I've been sleeping and the sun light coming through the windows I can tell when it's going to be time for me to go to work. This is when I would get these dreams that made me think that I was already getting up and going down to my car and leaving for work in the morning but, none of that was actually going on. My body was trying to move as if I was really living the dream but, in reality I was sleeping so I couldn't move which gave me that sick scary feeling like I was paralyzed.
My mind was thinking I was consious although really I was sleeping (what state are you in when sleeping? subconious?).