I have them all the time. One thing I have just found is Magnesium cream to rub on my shoulders, neck, spine legs, feet, anywhere. A family member has cancer and got the cream from a cancer center in Arizona for extreme leg & feet cramps. It does help relax the muscles and with the migraine pain that is at the base of the skull.
My muscles are constantly tense in my whole body all the time. When I realize I am squeezing the muscles I tell myself to relax just to find I am doing it again. The only time I am completely relaxed is in meditation.
My family member was told by the cancer center that you cannot take enough magnesium orally to do what the cream does. It can be compounded/made by any pharmacy if you can find one that will still do it. I am not sure if you need a prescription for it or not. The ingredients says "magnesium chloride 30% cream".