A/C Switches Randomly to Feet/Defrost?

2000 Dodge Stratus. Any time I use the A/C, I'll have it on face but it will randomly start blowing to feet and then to defrost and then back to face, etc. At first I thought it was only when I was on rough road that it would do it, but I'm not real sure on that anymore. Seems to just do it whenever. I'm hoping this is something with a cheap fix ?