Not sure if it's the same, but...
When I first started riding, I experienced a lot of pain in my shoulders. As it is, I already am susceptable to getting very tight shoulder and neck muscles due to stress (I carry it all in my shoulds) and ultimately that leads to major tension headaches. I had to spend a lot of time stretching my neck, shoulders, and back after each ride, and took a lot of long hot showers to make the pain go away. But, as I rode more, and the muscles in my neck and shoulders got stronger, I noticed that the pain slowly went away.
Do you experience tight neck/shoulder muscles at other times or just when riding?