How many miles on it? And are they highway (little shifting) or local (much
shifting) miles? Could be that the syncro-mesh widget on second gear is
dying. The second gear syncro is always the first to go, since that gear
gets the most shifting activity (going both up and down the gears). Unless
you blip the gas exactly right (or "double-clutch" properly) when
downshifting, you're calling on (actually, bashing) the syncro to mesh the
gears, so when it inevitably starts to wear out, you start feeling the gears
hitting each other slightly out of sync...
Replacing worn out syncros used to be a normal repair, but nowadays most
places would likely either not know how or simply not want to (since it
requires disassembling and re-assembling the transmission). Worst case, find
yourself a shop that specializes in tranny work (*not* one of the chain
automatic tranny shops).