You might know about snow angels but even if its not snowing outside you can make an angel on the wall. This exercise helps to loosen up your back and get you moving without the risk of too much pressure on your back.
Start by standing on the wall with your back flat on the wall. You can have your knees slightly bent or straight, the important part is keeping your back flat on the wall. Bring your arms up overhead by running them along the wall and then back down. Repeat 30 times and then come off the wall and feel stretched out, ready to go.