Is it possible to shorten 你叫什么名字? to 你叫什么?
"你叫甚麼名字?" specifically asking someone's name, which mean you are treating the person you are asking as a human; "你叫甚麼" could mean "what is your name" but it can also mean "what are you called" ;the answer to "你叫甚麼?" could be "Peter" or "The Devil". And worse, "你叫甚麼?" can be literally interpreted as "what are you yelling about?" or "why are you yelling?"

If you think "你叫甚麼名字?" is too wordy, you can use "什稱呼?" (how may I address you?)

Example: 

請問先生你叫什麼名字? (May I ask, Mister, what is your name called?) --> 先生什稱呼? (how may I address you, Mister)