Neck

When THE NECK IS TIGHT,THE MUSCLES ARE FIRING ACROSS THE VAGUS NERVE THROWING THE CELIAC GANGLION (WHICH DOMINATES THE DIAPHRAGM) AND MAY PUT IT INTO SPASM.  

A SIGNIFICANT SIGN OF THIS IS THE INABILITY TO  ABDOMINAL OR BELLY BREATHE.  MANY PEOPLE ARE LIMITED TO CHEST BREATHING, WHICH  DOES NOT PROVIDE ADEQUATE OXYGEN TO THE HEART AND BRAIN.  I HAVE SEEN THIS REPEATEDLY IN BELLY OR SIDE SLEEPERS.