Starting is the hardest part for me even after four years of it. Do something. A walk around the block is a great way to start. You will find that exercising helps get rid of that lethargic feeling and lifts your spirits as well, especially if you exercise outdoors. Make it a little longer/faster each day. Then add in another exercise type as an alternate to keep your body guessing--swimming, weights, pilates - whatever.
I like weights and pilates in addition to walking because it not only burns calories but also changes the way your body looks.
