How do you protect solar panels for storage during house rebuild?
Stacking the panels on top of each other should be fine, but I would not suggest stacking all off them on top of each other as the bottom one will have to bear tremendous weight and might warp it.

Try and place wooden battens (for air flow to stop moisture from being trapped and help displace weight evenly to the next panel using a soft surface) between panels on the same frame that they were mounted to the roof. The frame is load bearing and will handle weight on top of it and disperse weight downwards to the next panel.

You do not have to cover each one in bubble wrap. Just stack em using batons(bareing in mind weight) and then cover the entire stack in foil and possibly some polystyrene and or bubble wrap on the corners and top to prevent shock damage in case something hits or falls on it.. you never know.

Some panels you can stack ontop of each other with no problem as they have a robust frame that supports all the weight.

Exercise some common sense in how to stack them. Make sure they are level and aligned. check on them every now and again during storage phase in case the weight makes something give in.