Try googling "wall sit" it's an exercise that most doctors recommend for their patients to gently stretch the lower back.  All you need  is some wall space and a 10 minute break. Briefly, standing with your feet hip distance apart, lean back on the wall and try to relax not force your lower back on to the wall, eliminating the space between the curve in your back and the wall: do this by pulling your navel in. Keep the knees slightly bent, and just relax there for your break.

For purposes of releasing your lower back, you don't need to sit very low as in most descriptions, just keep the knees bent a bit.   However if you want to strengthen your legs you may go lower in the squat.

The worst thing that can happen is your fellow workers might think you are lazy.

Ask your doctor if this exercise is right for you.