Is saying to oneself, "O Qur'an, intercede for me," without uttering it, considered polytheism?

It is not permissible to supplicate the Qur’an and seek intercession from it, because seeking intercession is a type of supplication (du’a), and supplicating an attribute gives the impression that you are supplicating other than Allah, and this is shirk. However, there is no harm in wishing that Allah would allow the Qur’an to intercede for you.