Many people with neck problems wake worse in the morning.
If you have commenced your McKenzie exercises and are improving as expected, and yet seem to take a step or two backwards on waking and notice you are not as good as when you retired to bed, correction of your neck posture while sleeping may be required.
Often the issue is loss of the lordosis in the neck when your head protrudes forward on the pillow, or you flex your neck down towards your chest while sleeping.

Use of a rolled towel placed inside your pillow case or McKenzie Cervical roll (as in the youtube clip) will resolve the problem, and is often only required for a few days.

If after this your morning pain/stiffness is no better, it is likely that either the surface you are sleeping on, or inflammation (which accumulates with lack of movement over night) is likely the cause, and will need to be identified and addressed by your McKenzie Practitioner.