Sporadic refers to an expected behaviour occurring inconsistently. Let’s say we expect Tesla stock to go up every month, but instead, it goes up every quarter, then every month, then every quarter again.
This behaviour is sporadic as what we’re expecting to happen is what’s happening in an unexpected way.
Erratic means inconsistent and unpredictable relative to an expected pattern. For example, if we expect the price of bitcoin to go up, but it doesn’t, then that's a deviation from our prediction.
If it consistently remains inconsistent, it is erratic.
Chaotic is one step further on the unpredictability spectrum. Imagine if bitcoin left Coinbase or the price freezes, and then goes to $0.
This is chaotic behaviour as it is outside our idea of what is “expected”.