"Unpredictable behavior" refers to actions or conduct that is difficult to anticipate or understand because it does not follow a regular pattern, making it hard to predict what someone might do next. Full definition
Cats love to surprise their owners with unpredictable behavior, but watch what happens to a grey feline who plays what appears to be an empty plastic bag. (cattime.com)
Couples in conflict are often upset during counseling sessions; they may also argue, or make offensive comments or exhibit unpredictable behavior. (marriage.com)
For decades, breeders have made attempts at breeding their dogs as early as possible; the females who have become mothers too early often shown unpredictable behavior during and after the maternity. (breedingbusiness.com)