Hello
Stiffness in neck and shoulders seems at your age seems to be trapezitis which is inflmmation of the muscle you can feel between your neck and shoulder
Next Steps
It could be due to spondylitis which is a very broad term
Advise is not to bend your neck while working
Use comfortable table and chair to work
Ice the sore muscle
Tab myospas tablet twice a day after food
Use a spray or gel locally
Health Tips
Follow up with me with xray of your cervical spine ap and lateral view if pain persists
Take care