Again this is due to breathing faster than is necessary—carbon dioxide drops which result in tingling and tightness. Think of it this way. This response is very adaptive when necessary. Suppose you fall and damage your leg, where part of your leg has been cut open. In that case, your body will immediately get a stress response, and your muscles will immediately tighten.
Your body is trying to protect you, although getting this symptom when nothing has happened to you is understandably worrying.
During a Stress Response, the large skeletal muscles contract in the neck and shoulder muscles to prepare you for action. This contraction is what causes your neck, back and muscles to ache. It can also give you a headache.