Ignition key

I have Mitsubhishi 380 and I am having problem with its ignition system where the key goes. Sometimes when I turn the key, it won't start the car, I then move the key bit up or down and it will start the car. My understanding is that it has happened because I have a habbit to start the car while I am still standing out of the car(just to let the engine run a bit before I start driving) and it has made the ignition hole bit loose. Do I need to change the ignition? How much would it cost? Is there any other way ti fix it?
Thank you