solenoid,, next time you try to start the car and it won't start,, take a long bar such as a breaker bar or long stick and tap on the starter..
2.0 hype just bought his first Nx and he's had a heck of a time with it starting,, we replaced the rubber plug and switch, nice connections and still wouldn't start,, tapped the starter a few times and it started right up..
started 3-4 times in a row during the next few hours and then it did the same thing, No start, No noise, nothing.. tap tap ,, started up right away..
this Nx has been sitting for awhile and the only thing I can figure out is the corrosion and condensation is messing with the solenoid.. now for the last 5 days it has been starting up just fine....
good luck,, everything that could ever happen to our cars to not start,run,go go go has already happened to me a few times,, now it's just a matter of fixing it when it goes down and I've already had to do it once so it's no big deal to me.. I just hate to work on it when the weather is like crap..