What's happening to me in my sleep?

Over the past few months, on about 5 separate occasions I have had something very scary happen to me. Basically, when I am asleep I feel like I am having some sort of a seizure. It sometimes happens right when I begin to fall asleep, and other times right when I'm waking up (or it wakes me up in the middle of my sleep, I can't tell).

What it feels like: I get a painful electric shock in my brain as it happens and it causes my body to curl up in a fetal position and I bury my head into my chest. I lose the ability to control any parts of my body and no matter how hard I try to move, speak, or stop it, I can't. It usually lasts anywhere from 3-10 seconds and I have had it happen multiple times in a row, with the most being about 3 times in a row. I am fully conscious for them and can think and feel, and I can feel my body's movements (shaking like I have a cold shiver and then curling up) but can't control them. I simply have to wait until it's over before I regain control of my body.

The scariest part of when this happens is that the painful feeling I get in my brain increases very quickly until it "climaxes" and causes me to totally shut down. I feel it coming and it feels like my brain is going to explode and I get an extremely painful shock in right side of my head and then my brain feels like it totally shuts it off. It's incredibly scary because I go blank and sometimes get short-term amnesia and can't remember what even happened. It's like a brain power-cycle that I'm fully conscious for. The worst part is that it literally feels like death approaching, like my life is ending right there and I never know if I'm going to "come back" once the electric shock climaxes. And as I said above, this can happen 2-3 times in a row before I'm finally "freed" and regain control of my body. While this is happening I can't do anything, I simply have to wait until it finishes. I've found that the harder I try to get out of it, the worse it feels. Lastnight I tried my hardest ever to escape it, and I've had a faint pain in that area of my head all day, making me feel like it could happen again at any moment, except while I'm awake. I cried myself back to sleep because I thought I was going to die right then and there. I'm extremely scared to fall asleep again now because that's when it happens.

I can't emphasize the physical pain I get in my brain and the blackout that comes after. It starts like a tingle and then escalates like someone is turning up the electricity to my brain trying to make it explode. As I sit here now, over 12 hours after my last "episode", my head is still pulsing in that area and it is mildly painful. My body's physical reaction when it's happening is shaking and curling into a ball... the sensation forces my body into doing it. Sometimes it scares me because my head sometimes digs into my bed and forces me into very uncomfortable positions. It feels like someone is shoving my head as far down as they can, against my will. The scariest part being the end when it finally climaxes and my brain SHUTS OFF. I'm unable to think, I forget where I am, I feel like I've died. Then all of a sudden I'm back. It's over.

A few weeks ago this happened to me while I was sleeping with a girl. I had about 3 small ones in a row and she said I started shaking all over my whole body and curled into a ball and then stopped moving completely before waking up. I could feel it as it was happening and knew she was there, I tried saying her name along with "help me", but I couldn't open my mouth. She couldn't snap me out of it and neither could I.

The best way I can describe what's happening to me is sleep paralysis (which I've had in the past but am not afraid of or worried about) followed by a seizure that I'm fully conscious for. What is happening to me, could it be serious/life threatening, and what could be causing it?