  The idea of gauge theories of gravity predicts that there should exist not
only the massless graviton but also massive particles carrying the
gravitational force. We study the cosmology in a quadratic gravity with
dynamical torsion where gravity may be interpreted as a gauge force associated
with the Poincar\'{e} group. In addition to the massless spin-2 graviton, the
model contains four non-ghost massive particle species: a couple of spin-0, a
spin-1 and a spin-2. Supposing the restoration of the local Weyl invariance in
the UV limit and the parity invariance, we find the most general minisuperspace
action describing a homogeneous and isotropic universe with a flat spatial
geometry. We then transform the minisuperspace action to a quasi-Einstein frame
in which the field space is a hyperboloid and the field potential is a
combination of those of a Starobinsky-like inflation and a natural inflation.
Remarkably, thanks to the multi-field dynamics, the Starobinsky-like
inflationary trajectory can be realized even if the initial condition is away
from the top of the Starobinsky-like potential. We also study linear tensor
perturbations and find qualitatively different features than the Starobinsky
inflation, spontaneous parity violation and mixing of the massless and massive
spin-2 modes, which might reveal the underlying nature of gravity through
inflationary observables.
