Have your Magnesium and Potassium levels checked. They may be low enough to cause spasms. Google Magnesium and potassium deficiency..
Wishing you the best
It is probably nerve damage from pressure on a nerve where it exits the spine. Have you had low back pain now or in the past? You probably should see your physician about this. A nerve study and EMG (muscle study) could determine the cause of this.
Often happens from product which contains sugar. Wine, candy, fruit. Magnesium helps...get it checked by a doctor.