Well, more intimidated than outright afraid
Yes, intimidated, not wet-your-pants afraid.
Marines and other "manly men"
In this case, I know why I'm still intimidated now. I'm afraid that I'm not one of them, whether it be because they actually made it as a Marine (I simply quit before I got to that point), they can work well with their hands (I've never really tried), or they're "manly" (which I am, too, in a good number of ways, but I still worry about not measuring up).
Where it came from originally? My Dad isn't like the "average" Dad... no sports at all. Doesn't build things in the garage on the weekends. Heck, we didn't have a garage. He was a cop, but I guess I didn't get to see that much, and he'll downplay the "manly" aspects of it when asked, anyway. I mean, we did camp out a fair bit, with the Scouts, but I'm talking perceptions here...
Marines get to me. I wanted to be one, and I gave up on it. Intellectually, I realize that I'm probably better off with what I have, but facing someone who was able to actuate a dream of mine is a little daunting... like they already start ahead of me.
People with enough military rank (any service) get to me, too, although this is certainly something I've gotten over to a large extent. As the gap between their rank and mine diminishes, I gain confidence, but this is also from continued exposure and the realization that the rank doesn't make the man.
"Manly men." Guys with Harleys. Race car drivers. Rednecks/Good Ol' Boys. Men who work with their hands, can fix things, know their way around a car engine, who aren't afraid to get dirty. It's because I'm afraid they're better than me in some way. And I've tried to compensate, which isn't really getting over the fear so much as avoiding it in a fairly constructive way. I go out and do yard work (get dirty), do what I can with the car (thanks for the help for the obvious on the headlamps, SSG Geezer), and do as much as I can that a man should around the house. I do enjoy sports, I just don't have them very high on my priority list... but I've relegated that to be just a small part of my definition, as while I won't memorize a bunch of stats for it I can certainly sit down in front of the tube and appreciate a well played game (with or without domestic beer).
Some day... some day I'll be a man, I think.