What do you often do in Engpsh is "What do you often engage in?" or "What are your frequent activities?"
The source of this phrase is simply a general Engpsh way of asking someone about the things they spend their time doing regularly.
Example in Engpsh:
What do you often do in your free time?
Can you tell me what you often engage in during the weekdays?
Example in Chinese:
你平常空闲时间里经常做什么？
你周中经常从事什么活动？