I looked it up and a stiff neck is not listed. You slept wrong
I agree. A stiff neck usually results from sleeping....may have been how you had your pillow or the position you slept in. It will pass, try not to worry.
Are you having an increase in anxiety over taking a new medication dose? Anxiety and tense muscles could be the culprit.
Thanks for your responses. Neck is much better today. Not experiencing any increased anxiety over the new medicine. Thank you