Its nothing a serious problem Dont be shock its Just a bug ERROR.
but why this happen ?
1.It is a error issue happen whenever you recharge your xperia Z phone by unknown type charger and those charger gives your phone a harmful system voltage thatmeans occur ERROR to your phone both software and hardware for that a bad network service gives your phone earlier.
Extra method :- All of our electronics accessories run by voltage changing system into it but when we manually entired a deferent type of voltage its system do crash and ERROR happens something.
2.Whenever you gives your phone a Flight Mode option in 5.0 version of your xperia Z a bug ERROR Voltage enter into you phones system hardware area and manually do ERROR by this your phone restart again and again for that i suggest android 4.4.4 version that will release overheating problem from mmy eexperience never run stamina mode on your xperia Z.
3. Sometimes xperia Z showing "Sim card removed shuuting down" . It is a small piece of problem to solve this just open your phone back cover than remove battery from mother board than remove display flex cable than remove every flex cable from mother board and than try to remove the motherboard from your phone body than follow the sim tray for notice that any pin is out from the line if found repair it next wash every area of motherboard by Thinner and rebuild it into body and connect every cable than connect battery than power on your phone with sim card hope solve.
