  Solving the initial value problem for semiclassical equations that describe
two-dimensional electrons with the Dirac spectrum we found that collective
excitations of the electrons are composed by a few distinct components of the
oscillations. There always exist sustained plasma oscillations with well known
plasmon frequency $\omega_{pl}(k)$. Additionally there are oscillations with
the 'carrier frequency' $\omega = v_Fk$ slowly decaying in time according to a
power law ($v_F$ and $k$ are the Fermi velocity and wavevector). The reason for
onset of these oscillations has a fundamental character related to branching of
the polarization function of the Dirac electrons. A strongly anisotropic
initial disturbance of the electron distribution generates additional component
of undamped oscillations in the form of an electron unidirectional beam which
are van Kampen's modes in the Dirac plasma.
