May be your battery is giving problem so you should check your battery once. If possible then change the battery and then check whether the problem occurs or not.
Apart from this, if your phone turns off randomly without any reason then you can follow the below methods to solve it:
Solution 1: Check if phone is in Sleep Mode
Solution 2: Check battery status of your phone once
Solution 3: Stuck Power button
Solution 4: Boot your phone in Safe Mode
Solution 5: Search for the app causing error
Solution 6: Update phone’s software
Solution 7: Remove malicious virus from device
Solution 8: Check whether your phone is not hot
Solution 9: Do factory reset of your phone
