Hi @jibvi ,
Try starting the phone in [https://www.getdroidtips.com/boot-xiaomi-redmi-note-3-into-mode/|safe mode] and check if WiFi/BT turn on OK and remain stable.
''If they do'' then a downloaded app is the cause of the problem. The trick is to find out which one is the culprit.
''If still no good in safe mode'' try a factory restore (also known as a hard reset) and check if this resolves the problem.
'''''BACKUP''' the phone '''BEFORE''' performing a '''FACTORY RESTORE''' as it will ERASE all your data and downloaded apps.''
Once the backup has been completed perform the factory restore using the phone’s factory restore feature.
Once the factory restore has been completed check if the WiFi/BT turn on OK and remain stable.
''If still no good'' then you have a hardware problem.
''If the WiFi/BT are OK,'' restore the phone with the backup that you made earlier using the phone's restore feature.
Once the phone has been restored to what it was before, check that the WiFi/BT turns on OK and stays on.
If so then the reset has resolved the problem