Paralysis

Last night for the first time ever I felt completely paralyzed. I had taken a trazodone around 2000 and had woken at midnight. I played with my Facebook for approx an hour, then put it up and laid down. I was on my back which is different, as I usually curl to a side. Suddenly I felt weighted down and I couldn't move. I began to choke on my tongue and it took every bit of strength I had to move my tongue. Also I saw somebody hiding in the corner of my room. I remember thinking I'm going to die and I can't even yell for help. It lasted for ten minutes. When I could finally move I still felt like I was dragging weights. I do not think I am sleep deprived. However I am now afraid to lay down again. What happened? My therapist didn't know, however I was wondering if this is a sign of PTSD? How can I stop it from happening again?