Hello sstarbucks,
We'd be happy to offer a few suggestions on how to resolve this behavior.
First off, do you ever see temperature warnings on your device, telling you to stop and let the iPhone cool down before further use? If not, this article gives some great information on when your iPhone might be a bit warmer than normal and how to keep it within acceptable operating temperatures: If your iPhone or iPad gets too hot or too cold - Apple Support.
Additionally, we advise that you update your iPhone to the most recent iOS version and restart it once that's completed, then test the behaviors.
Restart your iPhone
“1. Press and hold either volume button and the side button until the power-off slider appears.
2. Drag the slider, then wait 30 seconds for your device to turn off. If your device is frozen or unresponsive, force restart your device.
3. To turn your device back on, press and hold the side button (on the right side of your iPhone) until you see the Apple logo."
Update your iPhone or iPad
“1. Back up your device using iCloud or your computer.
2. Plug your device into power and connect to the internet with Wi-Fi.
3. Go to Settings > General, then tap Software Update.
4. If you see more than one software update option available, choose the one that you want to install.
5. Tap Install Now. If you see Download and Install instead, tap it to download the update, enter your passcode, then tap Install Now."
We hope this helps. Let us know if we can assist with anything else at all. Take care.