There are signs Elon Musk may be getting cold feet a few weeks after he agreed to buy Twitter Inc. for $44 billion.

The billionaire Tesla Inc. TSLA -7.13% chief executive recently tweeted that the deal is “on hold” until he gets more information about the portion of the social-media platform’s users that are spam accounts. Twitter TWTR -3.72% has for years said in filings that it estimates they represent less than 5% of its daily active users, though has cautioned the number could be higher.

This is all happening as technology shares—including those of Tesla, which Mr. Musk is relying on to fund the deal—have been under pressure. Twitter’s board, meanwhile, says it intends to enforce the agreement, which calls for him to pay $54.20 a share.