Dear sir,
This condition is due to involuntary contraction of the muscles in that area. There are many causes of cramps, from dehydration to electrolyte imbalances.
Try drinking adequate water everyday. Exercise your neck and jaw muscles 2,-3 times a day.
During acute attack of the cramps, extend your neck above and massage the area.
Also, if possible do a blood investigation for serum
calcium and magnesium.