Car not starting!

Could you give a little more information, like the car type, model, engine, mileage, etc. Was anything done to the car recently, etc.

Once you get it started does it seem to run ok? Does it keep running without giving you any worries about killing?

I would start by hooking up a fuel guage to the vehicle and see if when it doesn't start if you have fuel pressure still.
Another thing you can try is tapping on the main relay when this problem occurs its usually a grey or black box about 4inches by 2 inches located either on the LH side kick panel or on the right hand side of the steering column.

Soory you think that because you're a girl you can't know about cars. Anyways I'll try and be a little more basic.
It sounds like an electrical problem most likely in your fuel injection system. Don't go"ugh" yet. The "main relay" I described to you earlier is if you look under your dash for the described box it will be stamped "main relay". From there knowing that this is the relay in question the next time the problem occurs you'll know where to tap. I worked on these cars for years and it sounds to me like that relay without looking into to it further. If it does start after tapping it you can change the piece yourself, just go to a dealership purchase a main relay, unplug yours and plug in the new one(that simple)
At the very most you might have to undo a 10 mm bolt to release it from your vehicle.
By the way where are you writing from, I'm from montreal!
GOODLUCK!

Just wondering how you made out with your no-start?

Thanks for the reply, hopefully it won't cost you so much in the futur!
So long from montreal!