Give it up. It was given to Nagato and not awakened. Its possible that Madara placed a seal that activated the Rinnegan that was given to him triggering the activation based on emotions,age, or who knows...We all just have to face the obvious. Didnt he just ask Tobi about Nagato recently with Tobi replying, "HE BETRAYED US."
Ask yourself "why would Madara who's been out for some time and just recently ressurected ask about Nagato?? To say "what's up?" Did he owe Madara money and is now trying to collect??
I believe you can figure out the rest.