iphone xs randomly reboots

When your iPhone shuts down do you receive any warnings on the screen?

This could be a battery or temperature issue

Keeping iPhone, iPad, and iPod touch within acceptable operating temperatures - Apple Support

iPhone Battery and Performance - Apple Support

Did the previous response help and fix your problem? If not, how’s your storage looking on it? I know plenty of people experience similar situation but it was because their storage was maxed out.

https://support.apple.com/en-us/HT201656

So, if the previous response didn’t help check your iPhone storage. I posted the link with the steps for you. I hope you get this fixed and I hope this helps!

Privacy is changed without my consent