I phone 7 getting hot

Excessive heating of an iPhone can negatively impact its battery performance, and this relationship generally does not work the other way around. Here are a few probable explanations:

1. When an iPhone becomes excessively hot, it can lead to accelerated chemical reactions within the battery. High temperatures can cause the battery to degrade faster, which ultimately results in reduced battery capacity and shorter battery life over time. This means you'll have to charge your iPhone more frequently and may experience a noticeable decrease in its overall battery performance.
2. To prevent damage from overheating, iPhones have built-in thermal management systems. When an iPhone detects that it's getting too hot, it may automatically throttle down the CPU and GPU performance to reduce heat generation. This performance throttling can result in slower and less responsive device performance while trying to maintain a safe temperature, but it's done to protect the battery.
3. While it's true that heavy usage or certain tasks like gaming and video streaming can generate heat, the primary source of heat in an iPhone is not the battery itself. Instead, it's usually the result of the CPU, GPU, or other internal components working intensely. The battery can contribute to heat generation if it's charging rapidly, but it's not the main source of heat.
4. Apple recommends avoiding exposing your iPhone to extreme temperatures (both high and low) to maintain battery health. Heat, in particular, is detrimental to battery longevity. Using your iPhone in hot environments or leaving it in direct sunlight can exacerbate this issue. Keeping iPhone, iPad, and iPod touch within acceptable ...
   1. Store the device where the temperature is between -20º and 45º C (-4º to 113º F). Don’t leave the device in your car, because temperatures in parked cars can exceed this range.
   2. Use iOS devices where the ambient temperature is between 0º and 35º C (32º to 95º F). Low- or high-temperature conditions might cause the device to change its behavior to regulate its temperature. Using an iOS device in very cold conditions outside of its operating range might temporarily shorten battery life and could cause the device to turn off. Battery life will return to normal when you bring the device back to higher ambient temperatures. Using an iOS device in very hot conditions can permanently shorten battery life.

In summary, while it's essential to be mindful of excessive heat and its impact on an iPhone's battery life, the battery itself isn't typically the main source of heat generation. Instead, it's the phone's internal components and usage patterns that generate heat, which, in turn, can affect battery performance and longevity. To maximize your iPhone's battery life and overall performance, it's essential to manage heat by avoiding extreme temperatures and minimizing resource-intensive tasks when your device starts to feel hot.

When I had a somwhat similar issue this is What I did...

1. Took a backup on iCloud (Which I do regularly)
2. Logged out of the Apple ID
3. Erase --> Erase iPhone - Apple Support (IN)
   1. Keep eSIM Data was the option I chose (See the pic)
   2. .
4. Set up my iPhone and restored it from iCloud Backup
5. 

I continued to have the same issue with the heating.

I repeated the above steps but this time I did not restore from the iCloud Backup. I set it up as a new iPhone.

Waited for 3 days. There is no heating issue, now.

Conclusion.:

• There is no hardware issue!
• This is not an iOS 16.0.3 issue
• Some Apps or iPhone storage and some settings may be heating up the device.

Action Plan:

• I will now slowly get my all data back one by one.
• Using the elimination process I will try to find out which app or settings were causing this...

Now the heating issue isn't there anymore. I am adding apps one by one and keeping tab on the heating issue.

My experience says this is purely caused by some third-party app that you may have installed.

I am not aware of the ambient temperature in which you are using the iPhone. However --> Keeping iPhone, iPad, and iPod touch within acceptable ...

Store the device where the temperature is between -20º and 45º C (-4º to 113º F). Don’t leave the device in your car, because temperatures in parked cars can exceed this range.

Use iOS devices where the ambient temperature is between 0º and 35º C (32º to 95º F). Low- or high-temperature conditions might cause the device to change its behavior to regulate its temperature. Using an iOS device in very cold conditions outside of its operating range might temporarily shorten battery life and could cause the device to turn off. Battery life will return to normal when you bring the device back to higher ambient temperatures. Using an iOS device in very hot conditions can permanently shorten battery life.

I phone 7 getting hot

iPhone 7 is > 6 years old, which also affects the battery life. The hardware remains old, so does the battery.

If it is still possible, have the battery replaced.

The battery can be replaced by Apple or an Apple Authorized Service Provider.

See this Apple article: iPhone Battery Repair & Replacement - Apple Support

If you are going to replace the battery, see -> Get your iPhone, iPad, or iPod touch ready for service

Get your iPhone, iPad, or iPod touch ready for service - Apple Support

The price is approx $ 69.

If you want to know exactly, call Apple directly, see Contact Apple for support and service -> Contact Apple for support and service – Apple Support (UK) 

or 

call 1-800-MY-APPLE

note:

You have to decide for yourself whether it is still worth having the battery replaced.

Try a force restart:

Force restart iPhone – Apple Support (UK)