Elon Musk, who was once fined $20 million by securities regulators for a single tweet about taking Tesla private, is taking a break from Twitter.

The billionaire co-founder and chief executive of the electric car company announced Friday to his 29 million Twitter followers that he was “going offline.”

An hour earlier, Mr. Musk, 48, said in separate posts on the social media platform that he was “not sure about good of Twitter” but that “Reddit still seems good,” referring to the popular discussion group website.

[Update: Elon Musk returned to Twitter on Monday.]

Mr. Musk, the entrepreneurial catalyst behind Tesla and SpaceX, the private rocket company and major contractor for NASA, represents a stark contrast from the usually tightly-controlled corporate chiefs on social media.