A stiff neck is generally not the result of any major medical condition, so fortunately it isn’t something to be too concerned about.
A stiff neck is brought about usually by the following:
Strain on the muscles
Sleeping with your neck unaligned, viewing a computer or tv screen placed at a non recommended level, carrying a heavy object on one shoulder, all of these are examples of putting your neck in an abnormal position, causing muscle spasms and fatigue. Even looking down for an extended period of time can cause stiffness, such as looking down at your smartphone.
Meningococcal disease is an example of an infectious disease, although rare that causes a “stiff neck” among more serious symptoms. If you are experiencing any other symptoms in conjuction with a stiff neck, contact a physician immediately
Cervical Spine Disorders
When any parts of the cervical spine shift from their normal positioning, this causes pain. There could be a problem with the facet joints, which can get progressively worse and pain and stiffness increase as a result. Facet joints are in the rear of the spinal segements, and they enable movement of the spine.
You could also be facing herniated discs in your spine, which aggravates the nerve roots. The pain caused by this causes pain or stiffness in your neck down to your arms. This is a more serious medical condition that requires treatment by a physician.