Bad answer:

Doing a good job and being rewarded for it.

It is not that this answer is wrong, it is just that it wastes an opportunity. This question is practically begging you to highlight your positive attributes. So do not give a vague, generic response, it tells them very little about you. Instead, try and use this question as an opportunity to give the interviewer some insight into your character and use examples where possible.

Good answer:

I have always been motivated by the challenge in my last role, I was responsible for training our new recruits and having a 100% success rate in passing scores. I know that this job is very fast-paced and I am more than up for the challenge. In fact, I thrive on it.