"Electric Shock" type pain in my scalp!

It feels like someone is touching my scalp with an electric wire or prod. Like a "zap" and then it takes a few seconds to get over it. It happens 2 or more times per MINUTE! It lastes for a couple of days usually and when it goes away it takes a few more days for my scalp not to be sore. I don't know how many times a year it occurs but when it does, like today, it drives me crazy. I walk around making weird faces and people stare at me. They think I have a headache or migrain but I don't, the pain is only on my scalp not IN my head. Sometimes the shocks occur over and over for a minute, then go back to 2 or more times per minute. It's the weirdest thing and I can't wait for it to be over. I never know when it's going to occur or what brings it on. Anyone ever heard of something like this?