I’ve also gotten a lot of unexpected leh cramps during night time when I turned 22weeks. It went on for a week. So I decide to up my water intake, as I read it’s an indication that you’re dehydrated. I also put my leg about waist level for about 15mins to help with blood flow. And take warm showers focusing on your tense muscles and soreness before bed. It helps a lot in subsiding the sudden leg cramps.
So far no remedy for this. It is normal for some pregnancy mummies. I had cramps on first pregnancy but not the second pregnancy. I just massage, use compression socks, during bath I soak with warm water.