Here are some of the few recommended steps that you should try when your iPhone XS crash.
1. If the issue only happens when you are watching videos on YouTube, force shutdown the app. On the home screen slide your hand from the bottom of the screen towards the top. Slide left or right and close the application and try again.
2. Restart your iPhone XS,a normal restart usually fixes this issue.
3. If the problem still occurs, go to your App store and check for any updates. If an update is available, download and install the update.
4. If your iPhone XS crashes only when you use a specific application to watch a video, uninstall and reinstall the app back again in your iPhone XS.
5. If you are still facing with your iPhone XS then contact the iPhone support.