Hi, we'd request you follow the below steps:
1. Clear system cache.
2. Try the same under safe mode:
Hold the power button for 5 seconds => When the screen flashes with option => Press & hold power option => You will get an option to restart in safe mode
3. If still you face the issue factory reset your phone after taking a full backup.
Please follow below steps may improve battery backup:
1. Enable “Power saver” (Settings > Power management)
2. Close apps that are not used (Bluetooth, WiFi, GPS, etc.)
3. Adjust sleep time and brightness (Settings > Display)
4. Boost memory when you see memory consumption is high with no app running,
5. check for background running applications, stop/disable unwanted apps, you can manage apps from auto-start manager.