I just started trimming (not shaving - I don't want to look like a 12 year old), and I've found that even with a minor trim - just enough to neaten things up, but not really enough to be noticeable) and find I get itchy from it. Scared the hell out me at first, because my first thought was "there's no way I got crabs, is there?" Fortunately there wasn't. I think it's from the clipped hairs being sharper than the natural ones. And they get turned around and stick into the skin. I don't like it.
But the advice above to exfoliate is excellent. I started doing that on my neck a couple years back, and since then I no longer have little bump irritations from shaving.
My advice overall, though, is stop shaving your hairs. The bush makes the man. Why do you want to look like a 12 year old anyway? You're a man, damn it. Have the courage to look like one.