He's nice then he's not and the cycle repeats itself. Why do guys do this?

Why would a guy pay special attention to a girl, help her out, and show all the signs of liking her, then turn into a total jerk and start being rude... only to go back to being nice again?
Then he worries that the girl might be pissed at him...
He's nice then he's not and the cycle repeats itself. Why do guys do this?
Post Opinion