Sometimes Late at Night

Sometimes, late at night, my legs suddenly feel like they're on fire. Almost immediately I start to twitch. The pain is so bad, My legs are under the crushing pressure of each other. The burning is so immense that it's actually cold instead of hot, and I start shivering. My torso feels like it's got a lasso around it, tightening and tightening, constricting my lungs and causing a pain in the middle of my back (like lying on a baseball with rusty nails). But it only happens when I'm trying to sleep late at night, not during the day, so we're still trying to figure things out.