Basically I'm looking to strengthen whichever neck muscles my left trap is compensating for. Whether they are just weak or if I need to re-establish a neurological connection to them.
I think it's my levator scapulae mostly that have become weak and stretched since the neck stiffness runs down to the top of my scapula. I haven't found any exercises that seem like they will be effective.
________________________How did I get here, in case this information helps.
I had a job that had me standing and looking at the ground right in front of my feet constantly. Probably 4 hours of looking down a day total. Often I'd bend down to pick something up, Lots of time spent in a pike position.
Over time my entire upper back seemed to just turn off. My stabilizers got stretched and weak; and my upper traps took over stabilizing my neck.
I started having shoulder problems and neck tightness.
One day I noticed my left shoulder was noticeably higher than my right shoulder.
I recently got kind of angry and decided that I'm going to start training again, and just started with a handstand hold against the wall 3 x 1 minute. The next day I had no tightness or pain. It came back though. Cat -cow seems to help too.
I moved out of that job and things improved to a point.
Currently my neck is always stiff, back of my neck feels overworked and my left trap is always feeling overworked. Shoulders are even again. No grinding or popping. Just can't figure out how to get some muscles to turn on and others to relax.