Iphone in loop of switch off and on

My Iphone XMax pro purchased over a year ago started showing unusual behavior since couple of weeks. All of a sudden, it started switching off and again switching on. While it switches on and i try to use something, its too slow and again switches off itself. And this continues on and on. I cannot even backup my photos to reset it. Is it covered by Apple to fix it even if its over a year. This type of issue should have warranty of more than a year. Software problem for a new phone recently purchased is so unsatisfying.