I've just read Isaac Asimov's Foundation series and in his novels Asimov always explains odd character traits but I haven't found it for Golan Trevize. Why is his intuition so reliable? Did I miss something in the books, has the author said it outside of the books?
Unfortunately, the source and nature of Treviz's talent is never revealed or commented upon.
The source of Trevize's intuition is not revealed. However, the reason for his intuition. In Foundation and Earth, Asimov discusses how the metaphysical relationship between intuition, the three fundamental laws and the larger universe.
It is a one in a really realy big nuber chance such a person is born whose intuition is always correct, he is that person. Born with the perfect intuition. Because of the size of the galaxy there is a possibility such a person could be born into the world.