Mitsubishi Lancer SE won't start

I have a 2012 Mitsubishi Lancer SE AWD. The car randomly won't start,
sometimes it does, and sometimes it doesn't. When it doesn't start I have
to get a boost and then it runs fine. It makes no sound when I turn the key.
I can go a week with no problems then out of nowhere it just won't start. I
had the battery and alternator checked and both are in excellent condition
and my mechanic says everything with the car is good. I change the oil
regularly and take it in for regular maintenance so I'm really not sure what
the issue is. I'm not mechanically inclined so any help would be greatly
appreciated!