Try 2 things: Check to see if you have any trouble codes and what they might indicate. Do a word search on here for "computer codes" to learn how. If you have any, write them down, let us know and we can tell you what they are all about.
Also try running your defrost and air conditioning through all the settings both at idle and under power on the road. See what causes what to happen when.
Most of all, don't worry. Usually it's something simple.
