Lenovo S850

Try press and holding on an empty space on your home screen, an option should pop-up, check the options there for auto arrange. Let me know if you find it.

Do you notice the time of it restarting? I found some phones with the option "Scheduled power on & off" in settings, maybe you have that too and accidentally enabled. Also, if the phone is heating up, that may be causing your phone to restart.

Hi Vijay. Can you try to install and use a vibrate testing app? In the past, there were people who had a similar problem, then they used a vibrate testing app and it started working fine again.

That's odd. Try reinserting the SIM slowly. Also, try to plug it to a properly working charger, check if that changes anything.

Hi Samantha. Yes, they should be able to fix your phone, the only problem there will be I think is availability of replacement parts. I suggest that you contact them first before visiting them.

Hi there. Does this happen to all the phone on the Wi-Fi network or does your phone experience this to any Wi-Fi networks? There are some factors to consider; distance of your phone to router, maybe the Wi-Fi network already reached it's allowed connections, wrong user and pass, or the Wi-Fi network is using mac filtering and your phone is not in the whitelist.

I had a phone with similar problem. It just randomly shuts off. What I did was replace the battery and it never shut off by itself again.

Same thing here... 

Hi there! Simply plug in the OTG device. Use ES file explorer as it works with OTG really well. If OTG device does not show up, then your phone doesn't support OTG.

I don't think it will ever get an update in the future.