In this scene, Macbeth goes to see the witches to try to get some answers about his future. I would say that his behavior during this scene is pretty erratic: it appears he's getting rather hysterical about the way events are unfolding.
When he first starts talking to the witches, he seems like he's in a frenzy. He's saying he doesn't care what the witches hurt; they just need to tell him his future or else.
Then when he thinks their prophecies are good, he calms down a bit. But then, the prophecy about Banquo comes up and he starts freaking out again.
In this second encounter scene with the witches, he is wildy erratic. In his first encounter with the witches he was cautiously optimistic. He sensibly realizes that their first predictions were correct, albeit he needed some help from Lady Macbeth. In this scene, he becomes widly erratic in his second meeting, but then calms down when he further realizes that they are correct again. It is his uneasiness with the issue of Banquo anddoesn't necessarily comprehend all of that this concerns, and he becomes agitated again. This characteristic of almost a manic depressive state fits well within the story line of the ups and downs of his character as a tragic hero.