sporadic

(of diseases) occurring in isolated instances; not epidemic.

Rare and scattered in occurrence.

It was a stodgy, weary display from Mourinho’s team with only sporadic moments when they threatened Salvatore Sirigu’s goal and their manager seemed bewildered afterwards when he tried to explain what had gone wrong.

Exhibiting random behavior; patternless.

Not belonging to any infinite family; an exception to an otherwise orderly classification.