How can I bake the normal map (Selected to Active) of an animation?

I need to bake the Normal map from a high res model that has shape keys on the timeline to a low res model using the Selected to Active option into the Bake panel. My problem is that I haven’t found any addon that can handle this operation and I have to bake manually any single frame of the timeline and save the images separately.
I was wondering about the possibility to write a custom script for this task but I don’t have any experience with coding and Python as well. Can someone help me to figure out this?