Ignition Kia Optima

KIA OPTIMA 2003.4 Cylinders, sometimes he does not want to turn on, if they turn on the dashboard lights but the start does not noise, the start, the relay, the ignition swich, the check, check and clean the cables of the bacteria at the start and the continuous problem, the curious thing is that it can happen until in month and the car does not fail and suddenly followed. I could have me, thanks ...