Battery heating issue on my iPhone 16 Pro

When you get a brand new phone, it can take several days for the phone to index all the millions of bytes of data it needs to index. At the same time you are likely doing what most people do with a new device and that is try it out for all sorts of things, like watching social media videos, playing games, trying out the camera, streaming music. And that means for the first few days, it will run warmer than you may ne accustomed to AND the battery won't last as long you imagined it would. This is all completely normal and after a few days, it will all settle down.

How long ago was the last update, which would have been iOS 18.4? You should expect excess battery drain and heat due to indexing of files and photo detection algorithms to recognize objects. After a couple of days that should be finished and will be faster if the phone is left plugged into power as this is done in the background.

If it has been more than a couple of days, then review the apps that are consuming your battery by going to Settings > Battery, and scroll down to see app battery consumption over the last 24 hours. Some apps will use background processes to consume your battery even when you are not using them. Meta has acknowledged bugs in their apps previously and suggested that an update would resolve the problem. For the most part the problems with the Meta apps has been reduced, but are still normally found to be the most problematic. This issue has been reported on Android phones as well and the Google Support site has been flooded with the same complaints for those apps.