If it took years to gravitate into a fitness level, then patience and determined focus can steer your body toward a different level. I would start with serious concentration on diet and nutrition as the background to build solid sleep and day energy. After that, go to what you enjoy and shape it into more of a workout. I agree with previous Wynn about not stretching early in any workout. I highly recommend swimming (total body, legs, stomach, back, arms, endurance) but get original and do whatever. I enjoy handling a basketball and do a workout, often during heat of the day, on a flat with no basket. Walking is no joke; I am a competitive runner and still weigh the same as I did when I was 20, but years ago discovered that walking ten miles tired me out as much as running. Along with other good advice in this thread, I would say relax, eat well, gradually yoga and stretch, and most important, amp up the things you enjoy into more determined exercise routines.