It's been reported that several customers over in the Apple forums are stating that their iPhone X is overheating
for no reason at all. Some have said they even put the phone in the freezer to cool it down and that didn't help. At this point in time it's too soon to say this is a wide-spread issue, but it's worth keeping an eye on. Also, beside the overheating issue, some users are beginning to suspect Apple is using some kind of enhancement that uses the cellular connection for some reason even if they have wifi turned on and connected. In addition to the overheating, some iPhone X owners are also starting to believe that Apple's new device uses a lot more cellular data than earlier models and that iPhone X "has enhancements that might use cellular data regardless of a wifi connection." Apple hasn't provided any insight into what those "enhancements" are or if they can be turned off but it could be quite worrying for individuals with low data tariffs who ensure that they stay connected to WiFi to stay within their data limitations.