1- The shoulder is traversed by a bundle of nerves, collectively known as the brachial plexus. Injury to the brachial plexus results in pain, usually the burning kind of pain, in the shoulder, neck and upper extremity.
Brachial plexus injuries typically occur when the head and neck are forced to one side, while the opposite shoulder is pushed downward. This motion causes stretching of the nerves of the brachial plexus.If you are practicing any kind of physical activity where this kind of motion happens frequently, then this must be the reason.
Possible signs and symptoms associated with brachial plexus injuries include intense, burning pain in the neck that goes all the way down to the arm and fingers on the affected side, associated with weakness and numbness in the affected-side arm.
Also, a whiplash injury (due to sudden forward "flexion" - backward "extension" of the neck), usually in the setting of a motor vehicle accident, can result in such symptoms.
Physiotherapy and anti inflammatory drugs are the 1st line of treatment. I advise you to get examined by a physician to identify the exact cause of your symptoms.