Alec Baldwin has quit Twitter, again. The hotheaded star signed off yesterday with a simple, “It’s been fun.” The last time he quit was after he was removed from an American Airlines flight in December. But a source said, “He just takes time off,” and will likely return. But Baldwin also shut down a fan who approached him for an autograph yesterday outside his Greenwich Village pad. “I’m just a fan,” a saleswoman from Brooklyn pleaded. Baldwin responded, “I’m very busy. Sorry, can’t talk,” prompting her to ask, “Is he really that arrogant?” Baldwin also told a reporter at a local organic cafe, “I’m having a private conversation, can you back off, buddy?” New wife Hilaria chimed in, “Please get out of my face.’’