ok try these steps.
Do a simulated battery pull by pressing and holding both power and volume down buttons for at least 10 seconds. Your phone should restart after this. Check if the issue still occurs.
To check if an app you installed is causing the problem start the phone in Safe Mode. If the issue does not occur in this mode then it could be caused by an app you downloaded. Find out what app this is and uninstall it.
Try wiping the cache partition of your phone from the recovery mode.
Backup your phone data then do a factory reset.