When was the last time you routinly exercised? If it was way back yonder, now is the time to get back to it. When people go from an extended period of inactivity and start doing very light exercise for a couple of hours per week is where someone makes the largest gains.
In other words if we were to both run an extra 2 miles per week (it would just be 2 miles for you), you would improve more then I would.
It's great you want to take the initiative to keep yourself in some shape, but maybe it's time for a real change of pace. Do you have 30mins at night to go for a jog? Start there, start slow and see how it goes.