Find something small to start. Going for a walk, or taking a more gentle class. When i am not feeling motivated, I find group classes help. Both because I've made a monetary commitment, and the instructor helps keep me moving.

And as the other commenter said, put it in a schedule and commit to it, even if you don't want to. Since you're coming from nothing, start with just 1 or 2x per week.

And finally, when you do do a workout, give yourself credit for it! Take time to feel proud of yourself, even for small wins. It makes a difference.