K.F.
Ok forgive me, because this is from personal experience but is it possible this is a control thing and he isn't afraid at all? Mine went through a phase where she was all of a sudden "scared" to do anything she didn't feel like doing, including nap. And there were times she would actually convince herself that she was scared, but it was more a battle of wills. . . . the suggestions below are good, we did similar things, but on top of that, we had to learn not to "play into it" if you know what I mean. "I'm sorry you are scared, but you are safe and it's nap time now". It just depends on their little personalities :-). Whatever the case, good luck. Naptime is precious!