10 speed Ultegra CS 6600.
When I march up and down the gears on the stand it shifts fine. If I test it on the road and march up down the gears it shifts fine. But on a ride if I have been coasting for a while and then pedal about 1 in 5 times it will jump a gear and then jump back (not a function of how hard I pedal - more random).
Chain, cassettes, and chain ring are all OK - not new but not worn out. Bike is 10 years old but it has new wheels and plan to keep riding it.
My thought is to replace the cables. What should I try before I take it to the bike shop?