Unknown intense pain in Calf?

On occasion I get an extremely intense and excruciating pain in my right calf. It feels like a fork has been stuck into it a rotated, like my calf muscle is trying to turn itself inside out. The pain usually last 2-5 minutes, but my calf will remain sore for 1-2 days afterward. This is not a frequent occurrence, usually months or even over a year or more can pass between this happening, but it almost always happens in the middle of the night when I am in bed and asleep. I usually but not always wake up just prior to the pain (I can feel the muscle is tensed up or tight).

I do not know what is causing this, I am a mid-30's male in good physical condition. It occurs regardless of physical activity in the days or days prior, it only occurs in the right calf, and is infrequent. However the pain is so intense I usually wake up those around me while coping with it. Pulling my toes toward my knee tends to help it pass faster, but intensifies the pain. I have had heat/stress/work cramps, this feels nothing like any of those.

Does anybody have any idea what this is or may be causing it?