It's very easy to build tension in the neck, especially if you are working on a computer or phone screen for long stretches at a time.
Try this remedy.
Imagine you have a glowing golden halo floating over your head. With the crown (top) of your head, slowly trace that halo in circles five times in a row. This is about slow, gentle motions.
Now go in the opposite direction. If you did clockwise the first time, do counter-clockwise the second time. Slow. Gentle.