Sounds like your a natural when it comes to driving efficiently (or did you get a little prior help the forum ). Did you get the manual or CVT? What was your last vehicle?
Auto stop feature only works under certain conditions. This can also be found in your owners manual.
-the temp of the engine coolant has to be near or at normal operating temp
-must have sufficient vacuum for brakes
-fan/ac must be off or have econ button on
-auto stop will reset when you travel above 10 miles per hour after your last auto stop