My Moto G4 gets really hot and starts to slow down...
And then I realize that I haven't closed a single application or window in the past 6 hours and I have 25-30% battery left!
In case any new phone buyers are considering this phone, that statement I made above has probably caused some people to buy it right away.
However, be careful of who you buy the phone from, because apparently the phones that come from Amazon can't be (and shouldn't have ever been) bootloader unlockable.
The only parts that got hot for me were the microSD card when copying apps to it, the space above that (the processor?) when playing Pokemon Go and Ingress at the same time, and the battery (which heated up everything) when I plugged the phone into the included turbocharger wall adapter. The camera only got individually hot once when I was installing another kernel.
The fix I found for the phone when it gets unusually hot (lots of open apps) is to carefully place it facedown on a flat glass or metal surface. I have an extra cutting board that I use when charging any device because even iPod nanos get hot when charging sometimes!