Fan turned on Modem, red light, internet not working

I have the newer xFi modem, with X1 

All has worked well for a couple months.

 

Today, the fan came on inside the modem, Odd, never happened before, not like extensive use or anything going on, just mild surfing.

 

A red light came on on the top, and internet quit, phone still worked, but no internet. 

 

I unplugged 5 minutes, plugged in, 5 minutes later, and all works as normal now.

 

What's the deal?  Will this happen again?  Do I need to exchange the router?

 

thanks