I've had these too......You have to play around with the cause.
I would do the following:
1. Black strap molasses ....if could be anemia
2. Lots of magnesium.....lack of magnesium. Better yet,
take a bath with 2 cups of Epsom Salt
and see if that
3. Salt load and drink tons of water....could be
When it happens to me, one of three usually does the trick!