If you are experiencing side effects such as muscle spasms, soreness, and chest tightness while taking Norflex for chronic neck and shoulder pain, it may be best to stop taking the medication. These side effects are not typically associated with Norflex, so it may not be the right medication for you. It would be a good idea to consult with your pharmacist about potentially switching to a different medication like Duloxetine. It's better to be cautious and prioritize your well-being.