Taking a systems approach it may not be a mobility issue.
Your sitting position/posture may need improvement
Episode 170: Death by desk? More powerful typing
Episode 109: The Neck of a Desk Warrior Poet
Jill Miller has some great quick fix videos on Yoga Tune Up that address the neck and upper back.
On the home page there is a link to get 1 5 minute video for free and the others are very low cost.