I am 28 weeks and got those cramps like about 4-5 times till now. All you have to do is massage that area slowly and pain goes away. My doctor suggested eat more potassium and calcium.
Hormones are higher at night, my theory. Try flex your toes when stretching at night, I get leg cramps at night to but if I flex my toes it doesn't happen as often.
It's normal, legs cramping is common in pregnancy. In my last pregnancy I would get them so bad it was like a lingering charley horse. This pregnancy I've had them a trick I've found to help is if you push your heal down like flexing foot flat. Don't point that toe, for me my leg would charley horse and spasm.