Although "te" is normally used to make reference to an action the other person makes on themselves, in this case it affects the meaning a little bit. ¿Y cuándo vas? = and when are you going? ¿Y cuándo te vas? = and when are you leaving? Hope this is helpful :) I am a native Spanish speaker so feel free to contact me if you need help with your Spanish.

in this case "vas" alone means to go and "te vas" means to leave