I'm using ellipsis in titles to ask the user. Something like this:
I have also this alternative (more traditional):
What do you think is the most intuitive for the user? Do you have another alternative?
I don't think this is about user intuition - it's much more about writing style and conventions.
The norm in forms is that the heading serves a category label to the adjectives/nouns below. So Car Features should do the trick here.
Another norm is to use imperative statements, but mostly for interactive controls (not labels), still you could also phrase it Choose car features.
I don't see much sense in "I have a car..." - it just doesn't tightly link to what's below and a clear misuse of this mark (and reminds too much of Martin Luther King).
You could always use a Mad Libs style:
I drive a [Color v] [Brand v].
Disclaimer: without more info as to what this is regarding, it's hard to say for sure. The following is based on gut feel.
"I have a car..." feels more appropriate when it's contrasted with other sections, like "I have a motorcycle..." or "I have a bus...", perhaps with a top heading of "What kind of vehicle do you own?" That makes it easy to find the section relevant to this particular type of vehicle being entered.
If it's just a general heading, I'd go with "About my car" or just "My car". Color, make (not brand) and model are generally not considered "features", as "features" has a specific meaning in the auto industry.
I don't see anything wrong with using a partial sentence ending in an ellipses as a user prompt if the answer you're asking the user to input is a natural ending to the sentence fragment in your label.
As you currently have it, the prompt and answers don't make a proper sentence:
I have a car...
Compare that with:
My car is a...
Now it works.
To make it work even better, the labels and input should be arranged such that they look like one continuous sentence when filled in. So, all on one line, similar font size, that sort of thing. You could even leave the ellipsis out altogether, and string the sentence together ("Mad Libs style", as @aslun puts it).
My car is a
But of course, you also have to think about your audience. The above is somewhat casual, conversational, and might feel too simplistic for some users who would be more comfortable with a standard form structure:
Why not use ellipsis to ask the user?
When you end the sentence with an ellipsis, it looks like part of the sentence is missing.
Ellipsis is mostly used to show the user the sentence is cut of.
Here is an example of a question were the ellipsis is correctly used: Best aesthetically solution to overflowing data in a table