People may be suffering neck pain with many reasons. The most common form of neck pain is caused by overstretching of muscles and spine due to bad posture.
When we sit and relax in a chair, the head and neck slowly protrude because the muscles that support them gradually get tired. As the muscles tire they relax, and so we lose the main support for a proper posture. This results in a protruded head posture and rounded shoulders.
Your neck is not designed to stay in a twisted position all night for hours. So if you choose to sleep on your side, use a pillow that doesn’t prop your head up too high, but aligned with your shoulder properly. And if you choose to sleep on your back, sleep with one thin pillow so your neck and spine are nicely aligned. The edge of the pillow may also be bunched up to form a firm support for your neck.