capricious

This term describes a volatile instability that feels arbitrary or whimsical. When applied to people, it suggests a lack of discipline or a tendency to act on impulse without a rational basis, often creating a sense of anxiety or unpredictability for those around them.

When describing inanimate forces like weather or markets, it emphasizes a chaotic lack of pattern. It differs from "random" by implying a certain fickle personality or temperament, as if the wind or the economy possesses a stubborn, unpredictable will of its own.