I have had this thing happen while I'm sleeping, but I feel like I'm almost awake & can hear what other people are saying, but I feel paralyzed and start to panic. Sometimes I even feel like my heart is racing so fast that I have to wake myself up or I'll die. I have panic disorder, and take Xanax for it. I've asked my doctor but he acts like he's puzzled or maybe he just thinks I'm paranoid! Anyway, it usually happens when I'm napping, and laying on my back. I'm just curious about what it could be.