Adding to Doug’s answer, the phrase could be used in any setting where a person is giving information to a group; e.g, a classroom, a lecture, a workshop, etc. even a video/zoom presentation.

Hi Yoichi, Usually someone takes questions after a press conference, for e.g. if a baseball player is switching teams, he'll read a statement then say to the room of reporters "I'll take a couple of questions." If you want to ask clients if they have questions in for e.g. an email, I would rather use 'answer questions', so "...but if you have any questions, I'll answer them now."

This would be a great question when used for live in person or virtual communication. It wouldn’t work for written communications such as email, any thing in print or pre-recorded videos as you can’t actually take the question “now” as you are not present when they read it. You could write something like: -Please don’t hesitate to reach out with any questions you may have. - Feel free time contact me with any questions. -If more informal: Questions? Contact us/me at ...

"take them now" means you really are available to answer now! So it's good for personal meetings like the other answers said. You can say "if you have any questions, do not hesitate to contact us" for example, for writing and emails.