I was and sill am a passive person, but when I stopped drinking, and like you, I became angry when I first began my recovery. And lost my job because of it. I was a chef that never yelled. Not many of us in that field of work can say that. Yet I also was usually drunk or high.
Emotions will be something that you will in encounter in a whole new way in sobriety. To help you find out why you are becoming easily upset you will need to take some time to look at yourself. In AA they use a tool of "inventory". Really this is a process that helps you identify many things in your life but anger is one of them. I say this because with the irritability you are having can be identified when it happens and you will be able to correct it. I in a sense police myself.
I can say after the months I have been sober I am much comer in tense situations and don't hold on to anger nearly as long. It is a process.