ive just bout a my06 wrx and sometimes it just wont start. you turn ignition on, put in the code, then nothing will happen.. turn the car off lock it, turn it on and it will start. doesnt do it all the time.. but has happen 3 times in 2 days since ive had it? the person i bought it off told me about it, and said i might need to get the pin changed?

any ideas? wouldnt just be a faulty relay or something