Age certainly has a role in your back pain, but I would move more towards your daily routine over a number of years as to why your current state is a painful and stiff one when waking up. Once upon a time when you were young and spry, you had less miles, thus there was less spinal compression and use overall upon your joints and structure. As time goes on, not only does gravity set in, but the repetitiveness of your job and habits lead to a creaky existence over time, similar to that of a car not being properly serviced. Also like an old car not being serviced, it has trouble starting in the morning, but once it gets going, it runs through movement. Keeping with this car metaphor, a car that is taken care of "properly" runs strong and powerful for a long time.
Your remedy is to do daily hip, spinal and shoulder mobility corrective exercises (based on your current postural position) to unlock your body over time. I say over time because it took you many years to attain your current state, thus change won't happen over night. If you start on this process, over time, your mornings won't be so painful and stiff. If allowed to re-find proper function, your body will find its way back.