Pretty much how it felt the first time, I freaked a little, my chest felt heavy and I was scared that I couldn't move, my body being paralysed but my mind buzzing with activity.
I actually got told this technique by a friend in high school, telling me I could "fuarrrk chicks in my dreams, it's so fuarrrking cool." That I did.
On the first time your description is pretty well how it is. Just blackness. Like when you close your eyes and just stare into the darkness.
However, I wanted to try again. So I did and this time when I felt that I was paralysed I simply started thinking random thoughts, mostly about sex…. But it worked, I just focused on those thoughts and not moving a muscle.
It's a strange feeling, like you are completely immobilised but could spring out of bed at any moment, you can almost feel the electrical impulses as you try to send them to your limbs to try and move them.
But all in all I just thought about something, and images started popping into my head, women, men. Sex. I awoke and felt as though I had just had the most wonderful, intimate sex imaginable.