In my production environment some SharePoint sites automatically blocked

To audit who blocked the SharePoint sites, you can use the audit log in Microsoft Purview. https://learn.microsoft.com/en-us/purview/audit-searchhttps://learn.microsoft.com/en-us/purview/audit-searchhttps://learn.microsoft.com/en-us/purview/audit-solutions-overview:

1. Sign in to the Microsoft 365 compliance site using an account that has been assigned the appropriate audit permissions.
2. In the left navigation pane of the compliance portal, click “Show all” and then click “Audit”.
3. On the Audit page, configure the search using the necessary conditions.

https://learn.microsoft.com/en-us/purview/audit-searchhttps://learn.microsoft.com/en-us/purview/audit-search.

https://learn.microsoft.com/en-us/purview/audit-searchhttps://support.microsoft.com/en-us/office/use-policies-for-site-closure-and-deletion-a8280d82-27fd-48c5-9adf-8a5431208ba5https://learn.microsoft.com/en-us/sharepoint/dev/general-development/how-to-avoid-getting-throttled-or-blocked-in-sharepoint-onlinehttps://learn.microsoft.com/en-us/sharepoint/troubleshoot/administration/access-denied-or-need-permission-error-sharepoint-online-or-onedrive-for-business:

1. Site Policies: SharePoint sites can be automatically closed and deleted based on site policies. https://learn.microsoft.com/en-us/purview/audit-searchhttps://support.microsoft.com/en-us/office/use-policies-for-site-closure-and-deletion-a8280d82-27fd-48c5-9adf-8a5431208ba5.
2. Throttling: SharePoint Online uses throttling to maintain optimal performance and reliability of the service. Throttling limits the number of user and admin operations to prevent overuse of resources. https://learn.microsoft.com/en-us/sharepoint/dev/general-development/how-to-avoid-getting-throttled-or-blocked-in-sharepoint-onlinehttps://learn.microsoft.com/en-us/sharepoint/dev/general-development/how-to-avoid-getting-throttled-or-blocked-in-sharepoint-online.
3. https://learn.microsoft.com/en-us/sharepoint/troubleshoot/administration/access-denied-or-need-permission-error-sharepoint-online-or-onedrive-for-business: If the permissions for the affected user aren’t configured correctly, or if there’s a mismatch between the account used to access the shared link and the account to which the sharing invitation was sent, access to the SharePoint sites could be blockedhttps://learn.microsoft.com/en-us/sharepoint/troubleshoot/administration/access-denied-or-need-permission-error-sharepoint-online-or-onedrive-for-business.