I am a 25 year old female and I have had this for about 15 years. My doctor diagnosed it as Restless Legs Syndrome.
http://en.wikipedia.org/wiki/Restless_legs
_syndrome
My doctor gave me a prescription called Requip but I had a very difficult time with nausea while taking it and I eventually stopped taking it because of this. It eased my symptoms but I would rather suffer the symptoms than having to get up in the middle of the night to vomit. I took the medicine for about a year and for some reason I don't get symptoms much anymore these days, only a couple of times a week. The only thing I've found that works for me is wrapping up very tightly in a blanket or wearing tight socks that go up to my knees. If that doesn't work I just deal with it until it goes away or I fall asleep.
Some of the causes could be serious or indicative of a more serious problem (like circulation issues), so best to see a doctor just in case.