Iphone Notch too hot to touch

Good day Tempest77, 

Based on your post, we understand that the top of your iPhone is getting warm when not in use. Just to clarify, does this happen while using your iPhone as well? Is your iPhone charging at the time? 

Here are a few things to check, in regards to the temperature. Let us know if any of this aligns with your situation. Keeping iPhone, iPad, and iPod touch within acceptable operating temperatures

Thanks.

Tempest77, 

From Settings > Battery, can you identify what's using the most battery? Is it an app you'd expect? Here's information on how to explore that and read the graphs and information, since it can break things down by time for you. This way you could see what's using the battery during those idle times. About the battery usage on your iPhone, iPad, and iPod touch

Thank you.

Tempest77, 

Since this happens when your device is idle, let's look a bit more closely at that time.

In Settings > Battery within the the 24 hours tab, during those idle times, you can use the graph near the top to break things down by hour. It will then show you which apps are using battery during that time, like overnight when your device would be idle and as you described, heating up. Are these the apps showing as using battery during that time?

If the situation is not present during that time, is there any difference? For example, though the device is idle is it connected to a different network, is Do Not Disturb enabled, etc?

Thanks.