Mössbauer spectroscopy study of magnetic fluctuations in superconducting RbGd2Fe4As4O2

57Fe Mössbauer spectra were measured at different temperatures between 5.9 K and 300 K on the recently discovered self-doped superconducting RbGd2Fe4As4O2 with Tc 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 RbFe2As2 and GdFeAsO confirms the self doping induced local electronic structure change. Surprisingly, we observe two magnetic fluctuation induced spectral broadenings below  ∼ 15 K and  ∼ 100 K which are believed to be originated from the transferred magnetic fluctuations of the Gd3+ moments and that of the magnetic fluctuations of the Fe atoms, respectively.