I purchased iphone 8 and facing multiple issues. My cell phone automatically switches off and then switches on. Sometimes becomes dead also and does not start unless reboot that. One of my friends said that there is some hardware problem. For last 2 months I am in talk with Apple service centre and support team and everytime they will tell you either to update software or they will record some log. Since every 7-10 days ios update comes so they will keep u engaged in this software update procedure citing this version will solve the problem and you will start tiring after hours long session with them after every 2-3 days.
It seems thick skinned Apple support team does not have intention to resolve the issue. End of the day you feel cheated after purchasing Rs 50K+ cell phone and perhaps moving to consumer forum is the only solution.