As you have another question about fatigue, I think these two are linked. See what your chiropractor says about your fatigue as well.
That's what I was kinda thinking too! It originally started about a year ago. It suddenly starts hurting, and just like that, it's gone again! It doesn't progressively get better... It just stops hurting! But, when it's "acting up" it HURTS!! It's the craziest thing. That's kinda why I was wondering if it's something that needs to get checked.
it sounds like a pinched nerve either cervical or upper thoracic of the spine. you neednt be aware of a certain motion you may have down eg: lifting, reaching the wrong way or simply twisting your upper body. find a good chiropractor. ( get referrences first !) he may give you good relief..I myself had what you have ! mine was a pinched disc.
Get yourself checked out by a physiotherapist! It could be a spinal disc displacement or ligaments and muscle tear.