  Using a combination of resistance fluctuation (noise) and dielectric
spectroscopy we investigate the nature of relaxor-type electronic
ferroelectricity in the organic conductor $\kappa$-(BETS)$_2$Mn[N(CN)$_2$]$_3$,
a system representative for a wider class of materials, where strong
correlations of electrons on a lattice of dimerized molecules results in an
insulating ground state. The two complementary spectroscopies reveal a distinct
low-frequency dynamics. By dielectric spectroscopy we detect an intrinsic
relaxation that is typical for relaxor ferroelectrics below the
metal-to-insulator transition at $T_{\rm{MI}}\sim 25\,$K. Resistance noise
spectroscopy reveals fluctuating two-level processes above $T_{\rm MI}$ which
strongly couple to the applied electric field, a signature of fluctuating polar
nanoregions (PNR), i.e. clusters of quantum electric dipoles fluctuating
collectively. The PNR preform above the metal insulator transition. Upon
cooling through $T_{\rm MI}$, a drastic increase of the low-frequency
$1/f$-type fluctuations and slowing down of the charge carrier dynamics is
accompanied by the onset of strong non-equilibrium dynamics indicating a glassy
transition of interacting dipolar clusters, the scaling properties of which are
consistent with a droplet model. The freezing of nano-scale polar clusters and
non-equilibrium dynamics is suggested to be a common feature of organic
relaxor-type electronic ferroelectrics and needs to be considered in
theoretical models describing these materials.
