Five moves, two minutes each: hip flexor stretch on each side, a seated spinal twist, shoulder rolls paired with a doorway chest stretch, ankle circles, and a simple neck tilt held on each side. Nothing that requires a mat or equipment, all of it doable next to a desk in work clothes.
I started doing this after a physical therapist pointed out that eight hours of sitting shortens hip flexors more than almost any other daily habit. Three weeks in, the lower back tightness that used to show up by 3pm most days had mostly disappeared.
Set a recurring reminder for midday, it’s easy to intend to do this and just never actually start.