Issues such as apps crashing, unexpected reboots, or fast battery drain could be caused by an app you installed. Use safe mode to start your phone with only the original software and apps. If the issues go away in safe mode, the problem is probably from an app you downloaded.
Do one of the following:

Touch & hold Power off. Then tap OK to restart in safe mode.
Use your phone and see if the problem has gone away. Remember, you won’t be able to use any downloaded apps.
If the problem goes away, an app is probably causing your problem, so you should exit safe mode and check your apps.
If the problem doesn't go away, an app’s not the cause. Try these performance troubleshooting steps next.
Press & hold the Power + Volume up buttons simultaneously, then tap Restart 
Or, hold the Power button for about 30 seconds, or until your phone restarts.
One by one, delete recently downloaded apps.
Keep a list of the apps as you go.
After you delete each app, restart your phone.
See whether removing that app solved the problem.