It is difficult without actually watching the clip of the show to get a better understanding of the true meaning of the person's words.

I found the line of the script from the show here:

http://www.springfieldspringfield.co.uk/view_episode_scripts...

I think there are two possibilities here,"to step" is American slang, see here for explanations:

http://onlineslangdictionary.com/meaning-definition-of/step

It can mean either "to fight/attack" or "to leave/step away", in this particular line of text it would seem more likely to be the former (to fight), but if you think about it, it could also be the latter if the person was being ironic perhaps.

The literal suggestions in Italian would be: Stai per fare a botte? or Stai per andartene?

Hope this helps.