One of the main things I see common with neck pain and lack of movement in the neck is the loss of occipital glide in the cervical spine. If we view the Occiput as the top, C1 is a circular ring of bone that sits underneath. When there is no longer free motion of flexion, extension, rotation and lateral bending, motion has been compromised.
The ability to have the combination of these movements becomes apparent when you passively move the occiput back and forth. There is often a restricted side and loss of flexion is the norm now with staring at computer screens and smart phones for hours a day.
When true motion becomes restricted we start to have to much rotation at segments below. This can create muscular attachments at these segments to become tense. Think levator scapulae and scalenes.
Restoring Occipital glide in many instances neurologically relaxes these muscles.
For the person being treated, working on keeping flexion in the occiput becomes something that should be focused on. Picture a string that is being pulled straight up from the top of your head with a very slight chin tuck. After you hold that position for a few minutes, keep that tall spine and slightly rotate about 20 degrees back and forth.
Occipital freedom plays a big role in how the cervical spine moves. Address it.