It sounds like you are describing a physical response to stress, which is a typical tensing of various parts of the body....some people will grind their teeth, others will experience an overall flushing and rise in blood pressure...while some will wring their hands, etc. Raising your shoulders also indicates to me, a sort of protectiveness mechanism you've unconsciously developed.
Once these have become habitual (consciously or otherwise) it is very difficult to gain control and conquer.....but it can be done. It requires that you become alerted to focusing on your body at the onset of what is considered "stress," to you. Ironically, by turning your focus to keeping your shoulders relaxed and in place, you will find your stress level diminishing somewhat.
I cannot stress strongly enough the importance of literally teaching one's self to "relax" their body....purposefully. Deep. slow breathing for at least 3 to 4 minutes is an enormous help. This too, requires focus to be done properly and do the most good. In a comfortable position, ideally in a relatively quiet space, concentrate on your respiratory system (lungs, torso, intake and out flow of air) and mental counting. Breathe in through your nose...s-l-o-w-l-y, until you feel your lungs filled to capacity....hold for 2 to 4 seconds....then begin to release this air, again s-l-o-w-l-y through relaxed pursed lips (as if blowing bubbles as children do)...Once you have emptied your lungs of this air....hold this position for 2 to 4 seconds also......and repeat this procedure for at least 3 to 5 minutes. Do not be alarmed if you feel a slight light-headedness. This is actually a good sign. Doing this each time you are stressed, will become habit and eventually help you to control the length and intensity of stressful periods. I promise you, this works with your cooperation and determination.
Working on "avoiding" stress to begin with....is another monster altogether!!