Since it is spasmodic, it is also commonly known as cramps by the common people.

The most common cause would still be low blood calcium. Therefore, you need to identify, are there any spasms in other parts of the body along with the neck cramps? The most common ones are for example the calves. If there are cramps in other parts of the body as well, it is definitely due to low blood calcium.

Also, is it caused by exertion or strain.

It is also important to identify whether it is caused by medication, such as long-term oral hormone medication or kidney dialysis.

There is also a need to identify if there is a stroke aura, or other brain disease that is causing the problem.

In conclusion, there are many possible causes for any illness in the human body. You should still go to the hospital for a checkup if necessary.