Apple devices heating up on setup or after a OS upgrade are nothing new. I suspect testing revealed the heat problem ahead of the iPhone 15 Pro launch, but Apple decided it'd be edge case enough to safely ignore for the product launch. Oopsie. https://appleinsider.com/articles/23/09/30/apple-confirms-ios-17-fix-for-overheating-iphones-is-on-the-way
@03a95182 I”m never surprised by heat issues within the first 3 days or so. I have been experiencing odd issues thereafter though. After morning routine (email, messages, notification checks) I’ll typically set my iPhone on my desk for a period of time between 40 to 60 min. On 4 subsequent mornings (not every one) after picking it back up it has been quite warm, more so than expected. I’m guessing there’s some fine tuning to be done and I don’t have Instagram on this phone currently. /1