One thing for sure. If it shook while you were sitting still, it's not the brakes. It sounds like the engine was about to die, as if it was only hitting on a couple of cylinders. This could have been caused by a fuel problem, electrical problem, or a vacuum line problem. If it did it once, and then stopped, my guess would be something quirky happened to the pcm/electrical signal, but after a few minutes it corrected itself. The MAF or a leaky vacuum line can also do this.
