Hello Sowmyaa Arun,
BitLocker can be configured to activate on its own under certain circumstances, especially if there are changes detected in the system that it interprets as potential security threats (e.g., firmware updates, significant OS updates, hardware changes, etc.). To retrieve your recovery key, you'll need to follow the steps in Find your BitLocker recovery key - Microsoft Support.
**Important:**Microsoft Support is unable to provide, or recreate, a lost BitLocker recovery key. If you can’t find the BitLocker recovery key and are unable to undo any changes that caused it to be needed, unfortunately, you’ll have to reset your device using one of the Windows recovery options.
Kind regards,
Lei