I have had a few of my iguanas respond this way over the years.
One was terrified of white plastic bags,another was frightened of hats and sunglasses while another was scared of my sons stuffed animals if they had large eyes.
What you describe sounds exactly the way all of mine responded to fear. Anything new in the house? Something thats changed? Do someone get a new hairstyle? It could be just about anything...
the only other thing I can think of is possible something causing acute pain, like a thorn or something but even then, they are such tough guys I dont know if they would react that way ..