OneNote does not have a built-in feature to automatically sort folders or sections in alphabetical order. The arrangement of notebooks, sections, and pages is typically manual, and any changes you make might not persist if the application is syncing or if there are issues with the notebook's location (such as being in an offline folder).
If your folders are rearranging themselves, it could be due to OneNote syncing with the cloud or conflicts arising from multiple users accessing the same notebook. Additionally, if your notebook is located in an offline folder, it may not sync correctly, leading to unexpected behavior.
To resolve this, make sure that your notebooks are not in an offline location and check for any syncing issues. You can also try moving the notebooks to a different location, such as OneDrive or SharePoint, to ensure better synchronization and stability.
If the problem persists, consider checking the settings or consulting support for further assistance.