First, take breaks! Roll your shoulders, stretch, wiggle & shake your arms around....
Another 'exercise' I learned that helps is "Yes, No, Maybe So"--- first nod your head up & down 3 times, like you're nodding 'yes', next turn your head from side to side 3 times - you got it, like saying 'no', and finally, raise your shoulders up to your ears & down again - 3 times ...'maybe so'!
Hope this helps!