Latest update fixes some overheating and camera lag issues, I recommend that you still have some random restarts after that update is to test if it happens in safe mode, if it doesn't occur there that most probably a 3rd party app is causing this.
1 random restart in 5 days is not an issue in my humble opinion, but if it's really bothering you, you can try to back up your data and perform a PC Companion Phone Repair. This will do a clean installation of the latest firmware and will also wipe your internal memory, thus eliminating any software glitches and erase all apps, then you can go re-install your apps gradually to see if one of them is causing this random restarts.
Open PC companion -> Support zone -> Phone/tablet software update -> Repair my phone/tablet (blue link style). Follow the steps given, do not connect your phone until prompted to press volume down while plugging USB cable.
I used iphone,it nearly not restart,maybe 1-2times over 3 months.So I think this device's restart is frequent.Sometime,I use a app,it restart.10 days ago,I just light the screen,this device light red and restart.It's very strange.......
