Alternative and related questions:
Do you have any reservations about your ability to undertake this job?
What reservations do you have about working for us?
The meaning behind the question:
You might think this is a reasonably innocent-sounding question but it's actually far from it! First of all, the interviewer has phrased the question in such a way as to imply that you probably do have some reservations and, secondly, asking you about any reservations you may have is clearly prompting you to disclose any weaknesses. Basically, this question is a bit of a trap. If you do have any reservations then they'll end up having reservations too!
Your answer:
In the previous chapter we covered the related question, "What reservations do you have about working for us?" This question may be rather different but the answer has to remain the same.
You don’t have any reservations!
More than that, explain to the interviewer why you don't have any reservations. As is so often the case, you need to turn the question round on them and convert it into an opportunity to sell yourself.
Example:
No, I don’t have any reservations about my ability to undertake the role. I trust I've demonstrated how my background and my experience have enabled me to develop the precise skills you are looking for and that I'm a perfect match for the job description you've outlined. I feel entirely ready and able for the challenge.
Word of warning:
If, in reality, you do have any reservations then now is definitely not the time to be discussing them!