The company’s directors are trying to rein in their unpredictable C.E.O. They were clearly blindsided by Elon Musk’s tweeting about his plans to take the company private, and several remain worried about his behavior. They have told him to quit Twitter — one even told him to stick to building cars and rockets. He doesn’t seem to be listening. On Monday, he tweeted that he was working with Goldman Sachs and the private equity firm Silver Lake as advisers.