Some kind of traumatic experience happened that caused you to relate that experience to doorknobs. I can only take a guess so an example might be that you were locked in a closet either as a punisment, by a sibling, or by accident. It could have gone on for hours and you were alone and in the dark. The only thing you might have been able to see was the doorknob, and your fear started to play tricks with your mind. Whatever it was, it was some kind of INTENSE fear that made you "project" your fear on the doorknob. A doorknob is an inanimate object and it is your memory of what happened that carried through to your adulthood. If you shut doors it may also be a fear of the dark as you don't know what's "in there". It could also be that you were an only child and when you were put to bed it was dark and scary for you. No one came to "rescue" you so you watched the doorknob but it became your "enemy". Or you had nightmares and your imagination again played tricks with you. I still suspect some kind of extremely traumatic experience. A doorknob is not your enemy...it is PART of a door. It is not "alive". Is is only an OBJECT. It's a tool that you USE to open or shut a door. Please be aware that I am not a professional psychologist. I have a degree in psychology but I cannot accurately diagnose your problem. I neither have enough information nor the credentials.