If it's a persistent thing, ask your doctor for a referral to a physical therapy place. Most insurances cover it and they can usually identify the problem better than a general practitioner can. He'd probably be happy to give you the referral-- most GP guys hate joint issues because they are so finicky.
Otherwise, look for repetitive activity. Knitting always
makes my neck/shoulder act up, unless I specifically schedule stretch breaks. It's not always a big lift type thing-- lots of little movements can do just as much damage.
Now for the controversial
Have you tried a chiropractor? It's one of those fields where some are totally bonkers and some are actually quite good, so it can take a few tries to find a good one, but I adore mine. The women in my family have always had back problems, but my chiropractor taught me a few stretches to do and my back is 10x better.
Long optional story: I was in an art class that involved me chiseling away at a rock. My back started to hurt, but I didn't put 1+1 together, and I went to my chiropractor and didn't think to mention it. She felt around my back and asked me "um, have you been stabbing something a lot?" I was all
and couldn't believe she could tell that from touching my back. But the field really isn't regulated well enough, so they tend to be either amazing or total hacks.