Waking Up d/t Mid & Lower Back Pain/Stiffness

I am having this problem for a while. I sleep at night and wake up after 3-4 hours of sleep with stiffness and pain in my lower and mid back. It is so bad that I have to leave the bed and then I walk or sit somewhere for 1/2 hour and then it gets better. This is going on for the last one year or more. I don't know why it happens. It gets better as day progresses. This is not letting me sleep for 6-7 hours. Is anyone having the same problem? Let me know if you know the cure. Let also tell you what kind of job I do. My job requires me to stay at desk most time of the day. My work place is an hour drive both ways. I am in mid-40.