"What do you want us to do for you?" or "What do you want?" This phrase is usually used when workers in restaurant or shop people ask the customer, "what do you want us to do?", Rather a vague way of saying. variation: 「何にいたしましょう？」: 主語 I/we 「何になさいますか？」 : 主語：you

AKIs explanation is perfect. In addition to that , we hear that sentence in the restaurant . a group members ask each other what are you goig to have? From a lower worker to the boss 何にしますか? From a boss to the lower worker 何にする? Between friends 何にする? I use 何にしますか? to my elder friends.