Agita is a feeling of anxiety, or agitation, like the agita your grandmother gets when she hears you and your brother arguing loudly over what show to watch on TV.
While agita is often used as a synonym for agitation, it actually derives from acido, an Italian word meaning "heartburn." You can use it either way, or both: "I'm feeling so much agita because I can't sleep after getting that terrible agita earlier from eating a whole bag of Doritos." In the mid-20th century, it was mostly New Yorkers of Italian descent who used the word agita, though it became more widespread by the 1990s.