Action is almost always driven by motivation, but sometimes, motivation is created by the action itself. Even if you don't have any idea of what to do, you tend to find out when you actually start doing it.
Should you ever experience a time when you can hardly find motivation, just do something—no matter how small or easy—to get you started. Even the slightest steps you take towards achieving your goal are important measures of progress, for it is these small actions that tend to drive you and keep you going.