  We study the time evolution of a system of fermions with pairing interactions
at a finite temperature. The dynamics is triggered by an abrupt increase of the
BCS coupling constant. We show that if initially the fermions are in a normal
phase, the amplitude of the BCS order parameter averaged over the Boltzman
distribution of initial states exhibits damped oscillations with a relatively
short decay time. The latter is determined by the temperature, the
single-particle level spacing, and the ground state value of the BCS gap for
the new coupling. In contrast, the decay is essentially absent when the system
was in a superfluid phase before the coupling increase.
