Why is my cat suddenly jumpy?

My cat is usually always extremely relaxed but all night tonight she was extremely jumpy as if everything was foreign to her. We haven’t moved, everything is exactly like it always is. Now as I’m typing this she’s in a cautious sitting position as if she’s waiting for something to happen and she starts to run and hide at the most tiniest of movements. Batting objects she’s slept on before and overall acting like she’s in another life. Her eyes are dialated and she’s in a constant state of fear. This is extremely unlike her and it’s starting to unnerve me as well. Any ideas on what is happening ?