Well, there are two "motivations" for a camera move -- one is to simply follow the action of the scene, so if someone walks from one place to another and you don't want to do it in cuts, you need to move the camera. The other is psychological motivation, like dollying into a tighter close-up during an emotional moment, or booming down / tilting up in a close-up to make someone look more powerful.
Movement and cutting are musical in nature, allowing you to create a certain rhythm to the scene. It's just like when writing poetry and using something like iambic pentameter, long, short, short, long, etc. Flowing movements puntuated by editing.
There are no rules. It's all about generating an emotional response in the audience and doing it at the right moments. For example, if you feel that a slow push-in has a certain effect of creating tension, you don't want to use that camera move on too many set-ups before you need it for the effect you want because you might drain it of its power.
There is also a power to the static shot, so it's not always a case of movement adding more emotion to the shot -- if used badly it can be distracting and therefore deflate the scene. Trouble is that no one can agree on when to move or to not -- that's where individual taste comes in.