Leg And Knee :: Fluttering Explodes Into Cramps In One Muscle And Spreads

I am suffering terrible fluttering in both legs below the knee, sometimes the back of the knee too. The fluttering then explodes into a cramp in one muscle which spreads to one or more others as I try to manipulate or stretch the first. The cramps are agonizing and last for up to 10 mins! When they finally subside the fluttering returns and the cycle keeps repeating itself. Rest and cold are sometimes factors. I would say I'm generally healthy and fit, I don't drink much water and sometimes I wonder if coca cola or diet coke make if worse. I have also recently done atkins diet but have been eating normally for a week or more. I can go weeks with no cramps then be plagued for a month! Its driving me mad and keeping me awake! HELP!!