Anyone who has trouble motivating themselves for exercise should think of playing a rigorous team sport they enjoy. When you enjoy it, it's easy to overlook the fact that it's even exercise.
I once lost 12 pounds during hockey training.
That's 12 pounds IN ONE DAY, mind you . . . while playing roller hockey outside for 6+ hours in 95-degree heat one summer -- and despite drinking about four gallons of water during that time, too.
Kids, don't ever try this at home. LOL.
I try, and that's what I have to work on. To me, a starting point is to admit to myself that I am inherently (physically) a lazy sonofabitch.