  We use Ehrenfest's theorem to provide a particularly simple derivation of the
{\em zitterbewegung} in the dynamics of initial Gaussian wave packets in a
two-dimensional electron gas. For initial packets which are very wide in the
$y$-direction, the {\em zitterbewegung} is only in the $y$-component of the
velocity. We extend our Ehrenfest theorem based calculation to the spin-orbit
coupled spinor Bose-Einstein condensate (BEC) to predict that there can be {\em
zitterbewegung} in the $x$-component of the velocity in this situation driven
by a combination of the nonlinear interaction in the condensate and the
splitting due to the spin-orbit coupling.
