Which are correct French translations of the question:

“Why do you follow me?”

(1) Pourquoi me suivez-vous ?
(2) Pourquoi vous me suivez ?
(3) Pourquoi est-ce que vous me suivez ?
(4) Vous me suivez pourquoi ?

Which one would you consider best?

Thank you.

The fourth one is not correct.

Number 1 is the most formal, then comes number 3, and the second one is colloquial.

Edit: actually even number 4 is OK when speaking. I’m not sure if “pourquoi” should be written as “pour quoi” or not… It’s not something I would write though.

I’d replace it by: Vous me suivez pour quelle raison ?
In this case the sentence is more formal.