I don't think there is an Plugin to that
You can contact a developer to develop your own plugin
In the meantime, I can suggest two methods that may be of use to you:
1- The user logs out so that he can ask his question anonymously.
2- You can use the q2apro Change Post Owner plugin, which enables you to change the user name of the question owner, for example, suppose that “John” asked a question, through this tool you will be able to change the question owner from “John” to “anonymous” or “username” specific".