Iron(III) nitrate and hydrogen peroxide reaction

When iron(III) nitrate is added to hydrogen peroxide as a catalyst, the temperature initially decreases and begins to increase after 30 seconds. Why is this the case? (is there any intermediate reactions of $$\ce{H2O2}$$ and $$\ce{Fe(NO3)3}?)$$

Nitrates tend to lower the temperature on dissolving, having a positive enthalpy change of solution. For example, $$\ce{NH4NO3}$$ has an enthalpy of solution in water of ~26 kJ/mol at ~300 K, and it is used in self-cooling cold-packs for that reason.
Sorry, I could not locate the enthalpy change of solution for $$\ce{Fe(NO3)3}$$, so this is not a definitive answer. You could measure that value, though, with some $$\ce{Fe(NO3)3}$$, some $$\ce{H2O}$$ and a calorimeter.