This is definitely an unknown in current scientific theory. No one knows how "natural" the evolution of intelligence is. Fortunately, you did not tag this question with hard-science, so we can make guesses!
We would need to define "intelligence" to answer the question. You saw this, and provided your definition: "...a life form capable of ask itself a question like the one I'm submitting right now." Excellent! Now, in proper form, I will suggest a counter definition which is hopefully inline with what you are thinking, but is easier to answer in biological terms. To do so, I would like to call upon an lyric from an old Jethro Tull song, Thick as a Brick:
The doer and the thinker, no allowance for the other.
This line always caught my attention. Those who do and those who think are put at odds. However, it does suggest a key attribute of "thinking" that I believe gets close to answering your question: it doesn't "do" anything.
Consider this as a model for thinking: the goal of thinking is to explore the time evolution of something (typically a model of the world around us), while isolating it from the rest of the world as much as possible while it is in motion. Once it ceases moving, we explore the results, and decide if we want to act on them.
A classic example of this would appear in combat. If you think about throwing a punch, you "throw it in your mind," and think about what will happen. Only once your mental punch lands, and you assess the idea, will you throw the punch. If it assesses poorly, you want it to have no effect on the world. Maybe you'll think up another punch to try. Or maybe a kick. The key is that when you decide what to do, finally, you haven't done anything. This means your punch is going to be very slow. To compensate, while we are thinking, we tend to do something we think is safe to prepare for the possibility of action. In combat, that's called telegraphing, and it tends to give your opponent an advantage.
So we see two major aspects here. First is what we just discussed, that intelligent thoughts are rather isolated from the world while they are in motion. The second is that we let them evolve in our heads, which takes time. The answer we get from an intelligent question is one which was valid several seconds ago. I think this is a key factor for the evolution of thought -- it will only occur if answering a question that's a few seconds old is still useful a few seconds later.
So this is where I believe evolution is natural. Evolution is natural in cases where there's value in capturing the "state" of something in the world, and playing with several futures in isolation before deciding how to act. For this to be natural, there have to be decisions to be made where the world isn't changing so fast that the decision is useless after the fact.
I think the manipulation of inanimate objects is the reason intelligence is natural. If the manipulation of inanimate objects to help you out is valuable, whether its using tools or building shelter, there will be value in developing intelligent thought. If the environment rewards spending that energy on responding to other creatures, intelligence may be less important.