The Difference in Body Angle
Mechanism / Why It Happens
When stationary, you can still ollie even if your weight isn't centered.
When stationary, you can adjust the angle of the board while keeping your body axis upright. Even if the board is slightly tilted, as long as your body axis remains vertical, the board will level out by the time you pop. While this may seem like a good thing, being able to ollie even when your weight is off-center can simply postpone the real problem.

What to Do
While moving, you can't ollie unless your weight is centered over the trucks.
When you tilt the board while moving, your body also tilts in the same direction. This is why it fee