  A stiff matter-dominated universe modeled by a free massless scalar field
minimally coupled to gravity in a Friedmann-Lema\^{\i}tre-Robertson-Walker
(FLRW) geometry is quantized. Generalized complex-width gaussian superpositions
of the solutions of the Wheeler-DeWitt equation are constructed and the Bohm-de
Broglie interpretation of quantum cosmology is applied. A planar dynamical
system is found in which a diversity of quantum bohmian trajectories are
obtained and discussed. One class of solutions represents non-singular
inflationary models starting at infinity past from flat space-time with
Planckian size spacelike hypersurfaces, which inflates without inflaton but due
to a quantum cosmological effect, until it makes an analytical graceful exit
from this inflationary epoch to a decelerated classical stiff matter expansion
phase.
