Dan Kotler is an archaeologist.
He is definitely not a secret agent but if it were suggested to him, his sense of humor would make him smile at the idea and likely shrug. What people thought of him had become of little importance over the years considering how often he was considered a quack and a charlatan by his fellow academicians, at least in the beginning. Being thought a government operative would have been a major step up from fool and crack-pot.
Kotler is definitely neither of those last things. He is immensely gifted and intelligent and has "PhDs in archeology, anthropology, etymology, and symbology. I also have PhDs in quantum physics and quantum mechanics," as he told an FBI agent who was questioning him. His love of research was made possible by the fact that he had inherited a sizable fortune and was good at investing. As a result, he was free to study what he wanted whenever he felt like it and was independent enough to be able to present theories that might have been suppressed had he been tethered to a university or a museum.
So Kotler considers himself a private researcher and with his financial independence and his extremely wide range of interests, he like to snoop. He loves a mystery, especially one that involved unknowns from hundreds of years before. Couple those traits with a love of travel and you get a man who can and will go wherever things look interesting.
Interesting things that he will go looking for and sometimes find seem to often include ancient legends of potent artifacts which attract not only researchers like Kotler but very rich and often very dangerous people who have far less than altruistic motives. These people or groups often enough have designs on power if not plans of domination on a global scale.
All this means that Kotler is not a government agent but he runs into enough of them to recognize them easily and, unfortunately for him, many of the not-so-nice ones know all about him.