Wasn't his last words. "I am Iron Man"?
Regardless Hydra coming back in a big way and being responsible for the death of his parents should add motivation.
He also says his armor "was never a distraction or a hobby, but a cocoon." That's kinda the whole point of the movie... He's not just some "man in a can," and Iron Man isn't the suit.
He's the Iron Man. He's the superhero. He doesn't have to be afraid of gods and aliens because he's the mechanic that can face whatever he's up against. Even when he meets the kid in the garage, the kid looks at the suit and says "Is that Iron Man?" And Tony replies "Technically, I am." Again... that's the point. To acknowledge who the real hero is.
So then, unless I'm totally wrong here, I'm willing to bet that he's done with going out and fighting, and isn't in the suit for a good chunk of the movie because what he can offer the Avengers and the world is his intelligence. So he makes Ultron, and very likely, he'll reluctantly suit up at the end to correct his mistake.