The cat and camel lower back exercise
This exercise is an excellent one to loosen up the lower back.
These are not stretching exercises.
They are fluid movements from one position to the other. Simply and smoothly, raise your back up as high as you can and then lower it back down as far as it will go into a sway back position.
This is not a fast moving motion, just go at the pace that feels the best for you. It should not hurt, not even a twinge of discomfort should be present while doing this exercise.