BLURR never stops moving. It's a habit he's gained over centuries of working as an undercover agent for the AUTOBOT Elite Guard. Constant mobility is the best way to avoid detection by DECEPTICON agents. He is used to remaining in vehicle mode for months or years at a time as long as it takes to complete his mission, learn what he needs to know, and escape. Unfortunately, because he spends so much time alone, he's not really used to talking so others can understand him.