Answer:
maybe you could go for a quick walk if you've been on the computor for a while, it might stretch your muscles. i think this is normal however; it's probably just because your body has been in the same position for a while. if you're really worried though, you should go to a doctor - they're the experts and they'll obviously know how to help :)
I would see a chiropractor. A lot of people think they are crackpots but they do know a lot about nerves and muscles that are associated with sitting in the same positions at work for extended periods of time. They can do heat and electrical massages/therapy to loosen up the tight muscles, and then "adjust" your back. (The adjusting I am skeptical about). They have the expertise to see if this does not help, and can order x-rays or an MRI to see about foraminal stenosis or a disc herniation.