Is somthing wrong with me? is this normal?

When I'm comfortable in my bed ready to drift off into my sweet dreams. All of a sudden I'm shaken awake. My leg will randomly jerk or kick out ward an it wakes me up. I wake up rapid heart beating an less tired then I was. I don't know why my leg does this. Sometimes it feels like the sensation I'm falling. Other times I'm so comfortable an I close my eyes an I'm violently awaken. It's pretty scary is it normal.
Is somthing wrong with me? is this normal?
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