Your daughter is pretty young, but it sounds very like tonsil and adenoid issues. I would take her to an ENT to check out her tonsils and adenoids. Sleep apnea caused by large tonsils and adenoids usually peaks around 3 to 4 years old, so if this is what it is, it may only get worse. Both of my kids had tonsils and adenoids removed because of this. My daughters at 3 1/2 years old.
We see Dr. Levinson. He is very good and does a "shave" technique with doesn't completely remove them, but "shaves" them down to a thin layer. The advantage to this is it doesn't expose the delicate muscles of the throat, causing less bleeding and a faster, less painful recovery.