Please try the following:
1. Check if your phone has recently downloaded and installed a third-party application. Uninstall it: Settings> Apps> See all Apps> Find the third-party application> Uninstall.
2. Check if the issue is to do with multiple applications running at the same time. Shut down and restart your phone regularly.
3. Back up any important data and restore your phone to factory settings.
4. Ensure your phone is updated to the latest firmware version. You can check if updates are available by going to Settings> System> System Update.
If the issue persists, contact the Nothing Support Team for further assistance.