2000 Camry Alternating Hot and Cold Air

Make: Toyota

Model: Camry LE

Year: 2000

Yesterday when i was driving home from work I noticed that the temperature gauge was almost to the top, i.e. very hot. I quickly flipped on the heat and put it full blast. This dropped the temperature gauge to a normal level. However, I noticed that the vent was alternating from hot to cold air every minute or so, like it wasn't able to sustain the hot air for some reason. I really don't know anything about cars, but if this sounds like something obvious I am all ears.

Thanks for any feedback!