iPhone 11 Pro Max turning off and on randomly and apps crashing on launch

Hello,

Has any other iPhone 11 Pro max user faced the issue that the phone turns off unexpectedly and turns on by itself. Also the software not updating and giving error and the apps not launching but crashing upon launch? This problem has been happening with my phone and I am really annoyed by this. Apple not helpful at all and on top of that there is no appointment with the authorised service centre.

Its apparently the best phone so far Apple has released and its been troubling me in the first year of purchase which is unacceptable.

Don't know what to do. Please help me.

Thank you.