my iphone xs keeps switching to silent mode by it self

Has the switch on the side moved?

I had an iPhone 11 Pro Max that had a bad switch where it would move by itself when jostled enough over time that was solved by having the phone replaced under warranty.

You may want to check your silent switch to see if it feels more loose or floppy than it should, and if it is and you are still under warranty it should be fixed at no charge.

If you are not under warranty, you should contact Apple Support directly and they will go over your options with you.

Contact - Official Apple Support

I am having the same issue. Tried all the troubleshooting including factory reset on phone. I can be holding the phone sometimes and see notification that it’s going into silent mode. I have to toggle the switch to undo it. Missed so many calls and messages because it keeps doing it randomly.

Hello,

Do you mean that the ring/silent switch changes to the "silent" setting? If so, "are you using a case?" Try removing it.

If not, try this:

1) Go to Settings > Notifications > Messages.  It is turned on?

2) Go to Settings > Sound & Haptics.  Change the "Text Tone" to a different sound.  Does it make a sound?

Note: you can send text messages to yourself for testing purposes.

Good luck.