Hi i've got the same problem. My phone is the A9191 model and im running the 1.32 software. My phone first started switching off last month. I removed the SD card, battery and sim card but that didn't work. Then I tried a factory reset which worked. The phone was running fine until Easter Monday when it started to turn off again. I tried a factory reset but this time it didn't work. Then I tried removing the SD card, putting it back in and trying a factory reset and that worked. So im guessing it's something to do with the software on the phone and the SD card.