Have you ever waxed it? If you decide to, use a cheese cloth to buff it out.
Wash it real good, then wax it, and then wax it again. If it's real bad use that turtle wax that has pigment in it. That actually works pretty good. It even takes swirles out of black paint. and again, buff with cheese cloth. It makes a huge difference.
Or you may try an oxidation remover if it feels like sand paper. Most of the time the wax will take care of that though.