not regular or continuous
sporadic - occasional
‘Sporadic’ occurrences of something only happen sometimes. There is no pattern to them, often making them random or isolated incidents. The term can be used in many different contexts ranging from the weather to the spread of a disease.
The weather forecast said that we should expect sporadic showers throughout the day.
It’s not mandatory for me to go to meetings, so I only attend sporadically.
The disease is still only sporadical, so it has not become an epidemic yet.