Iphone 6 automatic restarts sometimes and wifi grayed out

hello guys my old iphone 6 was damaged and from warranty they gave me new one. after that i have did backup from itunes then worked correctly fully clean and safe and yesterday i was played game everytime i played it and happend this apple logo screen off and screen turned on after that touch id not worked i entered password then unlocked i have continued thinked its nothing and saw wifi grayed out cant turn on turn off i did restard and worked correctly wifi enabled but after 4-5 hours same thing and again restart did. (not reset) worked correctly and now just 10 minutes ago same thing happend and if anyone knows its maybe problem of backup? from itjnes and after week happend this?? i have not tryed hard reset cus im in village now dont want to everything erased i tryed settings reset hard reset just settings and etc not deleted any app,game did you guys know something about this problem?! iphone 6 16gb ios 9.3.2 i cant update now in cellular... what to do? what is problem for this? sometimes opening app or playing game or just lock screen and apple icon then restart after restarts cant connect to wifi then im doing restart my iphone manually and corrects issue but i domt want to in 4-5 hours my iphone automatically restarted... p.s i yesterday i was taking selfie picture and it restarted please help me someone. Here is some pictures: