You will find that most stress relieving stretches are long, passive reclining poses. Small muscle groups are used to activate these stretches, but most do not require extensive use of muscle groups. One of the easiest and most relaxing stretches to remove stress is a simple roll neck stretch.
Place a cylindrical pillow or rolled blanket or towel under your neck between your skull and neck. Relax, laying flat on the floor, with the pillow under your neck.
I find it helpful to place my palms, face down, over my eyes. As you relax, allow air from your diaphragm to push slowly and gently against your neck so that it begins to roll over the pillow. As you feel your muscles unwind, allow them to release.
I carry a lot of tension in my neck and shoulders. In addition, I have the beginning of arthritis in my neck. As you lift your torso, using your hamstrings, press you shoulder blades into the floor and stretch your neck. Allow the pressure of your abdominal push and gravity to elongate your neck and spine.
Continue until you feel the tension in your neck, back, and shoulders release. This stretch can easily be done at your desk.
