  We investigate the impact of various fluctuation mechanisms on the dc
resistance at the superconducting resistive transition (RT) in epitaxial
titanium nitride (TiN) films. The studied samples demonstrate a relatively
steep RT with $\delta T/T_\mathrm{c}$ $\sim 0.002 - 0.025$ depending on the
film thickness (20, 9, and 5\, nm) and device dimensions. The transition is
significantly broader than predicted by a conventional theory of
superconducting fluctuations ($\delta T/T_\mathrm{c} \ll 10^{-3}$), which can
be can be tackled by the effective medium theory of RT in an inhomogeneous
superconductor. We propose that the underlying inhomogeneity has intrinsic
origin and manifests via two microscopic mechanisms - static and dynamic. The
dynamic inhomogeneity is associated with spontaneous fluctuations of the
electronic temperature ($T$-fluctuations), whereas the static one is related to
random spatial distribution of surface magnetic disorder (MD) present in TiN
films. Our analysis reveals distinct dependencies of the RT width on the
material parameters and device dimensions for the two mechanisms, which allows
to disentangle their contributions in experiment. We find that while the
$T$-fluctuations may contribute a sizeable part of the measured RT width, the
main effect is related to the MD mechanism, which is quantitatively consistent
with the data in a wide range of sample dimensions. Given the fact that both
microscopic mechanisms are almost inevitably present in real devices, our
results provide a novel perspective of microscopic origin of the RT broadening
and inhomogeneity in thin superconducting films.
