这个句子，仍然是看作省略了主语和be 动词（he was），假若说省略了he was going 也可以，意思没变。

Tom raised his hands as if (he was )to say something.

Tom raised his hands as if (he was going)to say something.

这样处理，既兼顾解释了本句，又不违背语法规则：

在某些状语从句中，当其主语跟主句的主语一致，而且含有be动词时，可以把主语（一般是代词充当）以及be动词一起省略。旨在使句子更加简洁和生动。

这个规则必须满足3个条件：（1）限于某些状语从句（2）主、从句的主语必须一致（3）有be 动词，这个be 动词可以是系动词，可以是进行时态的be，也可以是被动语态的be。

as if 方式状语从句中，省略“主语 + be”：

She talked to the stranger as if (she were) absent-minded. 她和陌生人谈话时似乎心不在焉。

He opened the drawer，as if (he was) in search of something important. 他打开抽屉仿佛要找什么重要的东西。

She stood at the gate as if (she was) waiting for someone. 她站在门口好像在等人。

The teacher shouted at the boy as if (he was) angry. 老师朝孩子大喊大叫好似很生气。

Tom raised his hands as if (he was )to say something.