I've noticed my Iphone XS gets warm even when doing very "easy" tasks, and it does this reasonably fast (a few minutes or so). It does not get hot, ever, only warm(er), and generally at the bottom of the screen. I have not noticed such a behavior on my other phones, including my previous SE. Have you had similar experiences with your XS? --- Post Merged, Oct 21, 2018 --- Just to clarify, I do not need to have any intensive apps in the background for this to happen and I've closed background app refresh (for other reasons). I've also tried taking bluetooth and airplay off. I live in a cold climate, although obviously it's comfortably warm inside, and I am using the official Apple silicone case.