Many patients complain to me about neck pain or shoulder pain. The pain is aching, throbbing or even burning. My doctor said "you have arthritis in my neck."
The most common reason, in my opinion, for neck/shoulder pain is poor neck posture. The muscles in the neck that extend from the upper back shoulder area into the neck is the trapezius muscle. It almost looks like a triangle on its side, with the wide base along the spine and the apex pointing towards the shoulder.
Poor neck posture or slouching occurs from people who do a lot of desk work; computer, reading, writing, etcetera. You're so focused on the material in front of you, which may be small font, that you voluntarily but not realizing, lean forward with forward stooping of your neck to come closer.
Now, imagine carrying a light bag of groceries and walk around. At first, it is alright, but the farther you walk, the muscles in your arm begins to ache. You stop, drop the bag on the floor and your arm pain goes away.
Basically, you are subjecting your arm to a constant strain that it is not used to or conditioned to handle, so you start feeling your muscle telling you that - pain.
The best treatments in this situation:
(1) Physical therapy that will strengthen the neck muscles
(2) Ergonomic adjustments at work
Massage and acupuncture are also helpful but provide temporary relief but does not treat the cause.
Muscles relaxants can be used, which may cause sleepiness and not treat the problem, so I am not a strong proponent of them.