All praise be to Allah.
To get back to the original question about intercession, I think it needs further clarification.
Dr. Booti explains it thus:
If one goes to a doctor, and receives medical treatment, and finds a cure to his or her illness, this cure should be attributed to Allah. The doctor is only a means by which Allah cures His servants.
If a person thinks that the doctor himself cured him, then this is a type of shirk. Harm and benefit come only from Allah.
Likewise, Dr. Booti explains: if a person receives intercession on the Day of Judgment, this is a result of Allah's Mercy. Allah may choose that the vehicle for His Mercy be His Prophet (peace be upon him), or the Quran, or righteous actions. They are the means that Allah chooses to show His Mercy to His creation.
However, if a person believes that Prophet (peace be upon him) is the one who actually grants him success in the afterlife, then he has committed a type of shirk.
End of comments by Dr. Booti.
I hope this makes things clearer
May the peace and blessings of Allah be upon our beloved Messenger Muhammad, his family, and companions.
And Allah knows best.