MY IPHONE XR SHUT OFF AND WONT TURN ON

Try a force restart. This link tells you how --> Force restart iPhone - Apple Support

I just bought my iPhone XR less than 3 months ago -brand new and this week it has overheated and shut off three times. I've done all of the suggested things to do. i think it's time to bring it in to the apple store.

Yes, if it's overheating, have it looked at - that's not normal.

Genius Bar Reservation and Apple Support Options - Apple