Stretching regularly, with movements like neck flexion, is a good way to relieve tightness and reduce pain in this vulnerable area.
Pain can have a sudden onset - for example after a car crash or a fall - or can come on gradually. In either case you should consult your doctor, but once you have been cleared for normal activity, then stretching can do much to reduce pain.
Neck flexion is a basic exercise that you should perform regularly if you have any cervical symptoms - or indeed, numbness running down the arm.
You can do it standing or sitting - the position isn't important, as long as you are comfortable and relaxed.
Begin the exercise by bending your head forward, allowing your chin to drop towards your chest. Stretch until it feels tight, hold for 5 to 10 seconds, then gently raise your head back up.
Do this ten times, and feel free to repeat it several times through the day.