I'd agree with everyone else--please do not take the MCAT without preparation. At the very least try to take at least one online MCAT through AAMC (they offer one for free). I ended up doing really well on the MCAT but my first practice test was around a 21. Even if you know your material well there's a very good chance you could score in the low 20's.
The MCAT isn't an apptitude test like the SAT, it's based on how much knowledge you have. If you didn't just complete your pre-med courses it would be a really good idea to at least review the material.
Your score does depend on how many questions you answer correctly, but if I'm not mistaken it also depends on how many questions others answer correctly (that way if a certain test is harder than others, it is taken into account when giving you a score)
A big part of the MCAT is knowing how to take the MCAT--it's known for asking questions that are addressing basic science topics yet appear to be asking about something you'd encounter in more advanced courses. I can't remember if it was on a practice test or the real one, but I remember a question addressing particle accelerators. That sure scared the beejeebers out of me until I told myself "the test only asks about things I learned in my pre-med courses, so I can answer this!" I think a big part of taking the MCAT is learning to not be afraid of it. It won't ask questions where you need to understand quantum physics (but it might look like it!)
Honestly your approach of not worrying about the test is an asset--but I think that could greatly be offset by not preparing. I think it would be ideal to both prepare and not worry--I can guarantee that your experience will be much more favorable!
Honestly, you should take the MCAT when you feel ready. If you feel ready now and are set on taking the MCAT without preparing, then I doubt anyone's opinion will stop you. But it really is advisible to take the MCAT once and only once. If you did poorly the first time and then got a 35 or higher then your low score would certainly not help you. But some or most schools look at your highest score. But they will see all your scores, and if they ask you about why you did poorly on your first test and you say explain how you decided not to study or prepare for the test, your interviewer will almost certainly question your maturity and dedication to becoming a physician.
Also, not everyone gets a 35. If you feel you can do it--but why not get the 35 now?
Good luck with whatever path you decide to take! (But still, please study!)
-Brent