  $^{57}$Fe M\"ossbauer spectra were measured at different temperatures between
5.9 K and 300 K on the recently discovered self-doped superconducting
RbGd$_2$Fe$_4$As$_4$O$_2$ with T$_c$ as high as 35 K. Singlet pattern was
observed down to the lowest temperature measured in this work, indicating the
absence of static magnetic order on the Fe site. The intermediate isomer shift
in comparison with that of the samples RbFe$_2$As$_2$ and GdFeAsO confirms the
self doping induced local electronic structure change. Surprisingly, we observe
two magnetic fluctuation induced spectral broadenings below $\sim$15 K and
$\sim$100 K which are believed to be originated from the transferred magnetic
fluctuations of the Gd$^{3+}$ moments and that of the magnetic fluctuations of
the Fe atoms, respectively.
