Please try the following:
1. Open the auto-start Settings page and cancel the auto-run application. Note that some models have no auto-start option.
2. Uninstall any applications that you don't use much.
3. Ensure your phone is updated to the latest firmware version. You can check if updates are available by going to Settings> System> System Update.
4. Back up any important data (such as contacts, text messages, etc.) and restore your phone to factory settings.