The rare earth titanates and stannates cristallising in the pyrochlore crystal structure are prone to magnetic frustration effects due to the topology of their lattice. We have recently shown that the Nd2Sn2O7 pyrochlore orders in a so-called all-in--all-out magnetic structure, and that its dynamics is anomalously slow in the paramagnetic phase. We associate this feature with short range correlations that have been evidenced in several pyrochlore systems especially from neutron scattering experiments. We have partly characterized the slow dynamics of Nd2Sn2O7 in preliminary muSR measurements. In particular, the temperature dependence of the fluctuation rate suggests that clusters of spins rather than individual spins are at the origin of the slow dynamics. To ascertain this interpretation, we need to complete our experimental data.