With over 100 million iPhone 15 series in use, I’m sure that there are others with similar symptoms. As far as getting “heated up” all smartphones will get warm in use; it’s called the 2nd law of thermodynamics. As long as it doesn’t actually overheat and shut down it is operating normally.
if you fast charge your phone may get very warm, pause charging at 80% and display a message saying that charging has paused, and will resume when the phone cools down. This is NOT overheating, and is normal when fast charging. It also won’t prevent you from using any app you have on your phone.
If you are having sound problems see→If the microphones on your iPhone, iPad, and iPod touch aren't working - Apple Support
Also, some apps that use a lot of energy or that use cellular data rather than Wi-Fi can cause the phone to run warmer.
And if this is your first phone with 5G networking, 5G uses more energy than 4G/LTE, and will get warmer when using the cellular network.