no no no, flicking cannot be instantly put down to ich - where ever you read this is wrong, flicking is caused by so many things and can be the first symptom of many diseases, caused by ammonia or NO2 spikes, temperature changes, fights, knocks and scrapes, parasites, bacteria, fungus, the list goes on and on.
But you can be sure it is not a good sign, usually the first sign of something wrong, if the fish scratched itself then theres not much need to worry but it could be a sign of parasites or worse. This could well be ich but simple flicking is not the way to diagnose it.
Unfortunately if flicking is your only sign and water parameters are perfect the only way to find out whats wrong is to keep a close eye on them and watch out for any visible signs of disease and keep a very close eye on water conditions, make sure the water is well aerated and feed a healthy varied diet.
If you have test kits could you please post water stats: PH, ammonia, nitrite, nitrate, KH and temp.
Also please post tank size and fish.
Jonny.