If I stub my toe four times at random intervals over the course of a year, it's not intermittent toe-stubbing.

It's not sporadic toe-stubbing either; or at least I wouldn't use that word to describe it.

You are free to make that distinction between 'intermittent' and 'sporadic' if you like, but I don't think that distinction is as standard a part of the meanings of those words as you think.