It may be due to cervical spondylitis
Please get an x-ray done of cervical spine first.
Do some isometric of neck.
Hot water formantation at back of neck and shoulders
It may be due to bad posture,
Next Steps
Take a Rhumasyl oil for gental massage on neck and shoulders
Avoid jerky movements and forward bending
Keep your posture correct always during work and using mobile phones.
Health Tips
You may take ultrasonic therapy at physiotherapy clinic for 15 days
Thank dear,
Get well soon