Thanks for your question.
If the sounds are clicking or cracking in nature and occur when you move the head, it may indicate sustained contraction of the neck muscles, which is the commonest cause of such sounds.
Other causes of such neck sounds include bulging of the disc between the bones of the spine(vertebrae) at the neck, sprain of the ligaments involved in connecting the joints in the spine, and certain problems with those joints.
The problem with the sustained contraction of the neck muscles is that it pulls on the bones of the spine in the neck region, such that when you move the head, the pulled bones rub on each other producing those sounds.
Such muscle contraction may be caused by stress, neck injury, muscle strain, and poor neck and body posture.
However, I would strongly suggest that you pay a visit to your GP to examine the neck and refer you to the appropriate specialists for an accurate diagnosis.
I hope I have answered the question and provided some clarity on the issue. I'd be glad to respond to any more questions you've got.
Best wishes.