I've experienced this more times than I can count. It's always really scary! The worst part is that sometimes I will have dreams that I'm in water and I'll actually hold my breath in my sleep, and wake up gasping for air. That seems to happen a lot less often since I switched to a much healthier diet and started healing. (I was tested for sleep apnea, they said I don't have it)
The most recent episode happened this past Monday. I don't work Mondays, so I was home alone at my boyfriend's house while he was at work. I was watching a movie on his bed and I passed out - I was just feeling really tired. This was around 1-2PM. I was half awake (eyes half open, couldn't really move) and was lying on my side facing the doorway to his room. To my knowledge, everything looked as it should - it was daylight, his room looked the same, was just partially awake. Suddenly, my bf barged in to the room like he usually does and walked right over to me. I thought it was weird, because he told me he wasn't coming home for lunch. First he walked past me to check the air conditioner, then he came over to me to wake me up. He put his fingers on my neck to check my pulse, because he could tell I was in that half awake state. He asked me if I was okay and tried to wake me up. I didn't believe it was really him, so I was struggling to wake up. I tried to kick/slap him with my arms to see if I hit solid leg to prove that it was really him and I wasn't dreaming. I *hit* solid leg, or so I thought. When I eventually fully woke up, I realized that I was alone and that he never came home to check on me. I texted him to double check (it was so real) and he confirmed he had not come home. I do count this as sleep paralysis, because I was partially awake, not fully asleep, and I was really trying to wake myself up. Even though it could have been much more terrifying, it was really disturbing...it was so realistic but yet I still knew it wasn't him and tried to prove it, and somehow my brain tricked me into thinking I hit solid leg and that he -was- really there. So freaky.