Anyone ever have sleep paralyzation happen to them?

It happens to me often . Its were Im supposedly asleep yet fully aware of whats going on around me and I cant move my body. Its actually scarey as sometimes Im left in this state for ages . I found out how to escape from it by shaking my head left and rigth till I wake up. I found this by telling some guy once about my sleep paralyzation and he told me that some peoples bodys kinda switch off during sleep but the brain is kinda left in standby mode . I used to read a magazine called X Factor which one day made a request for people that suffer from this and I contacted the professor , Its a lot more common than I thought.

Any one suffer from this?