Hi Mieke, I get this several times a week, and it is very hard to shake off. I find a mixture of pain meds, muscle relaxant and rest is the best.
My pain dr thinks that mine is probably caused by a very tight muscle that runs from the neck to the shoulder. It does all get sore together so I think he's on the right track.
Will be starting a special exercise/ stretching program soon to improve overall muscle tone and see if that does the trick.