you're probably giving it too much gas out of the gate and spinning the tires to the point where you're getting wheel hop-- thats the only thing i can think of that feels like what you're discribing.

:edit:

yeah, and now that i think about it with the tires they put on these things this could be what you're feeling... otherwise it might be a broken engine mount, which i don't see happening here because it only happens every once and a while.


your wife just may be taking it a little too hard on the gas