He must be going soft in the head.

他一准是脑子出毛病了。

《牛津词典》

I must be going now.

我现在得走了。

《牛津词典》

I must be going home; it's way past my bedtime.

我得回家了，早过了我的就寝时间了。

《牛津词典》

Here is an example, called "Hello,I Must be Going."

VOA: special.2009.07.19

I wish I had more time, but I must be going.
I wish I had more time, but I must be going.

I wish 课堂 - SpeakingMax英语口语达人

So, what must be going on in swap?

那么，在swap中发生了什么呢？

哈佛公开课 - 计算机科学课程节选

So on the rare occasion when Merkel says something vivid, something important must be going on.

CNN: Germany's Merkel is right -- multiculturalism has failed

But she conceded that the price must be going up to reflect the price rise of the underlying materials.

FORBES: The Oscar gets more expensive

This is almost unprecedented in an advanced nation outside of a major epidemic so something must be going seriously wrong, right?

FORBES: Life Expectancy Is Falling For U.S. Women