Which condition is described as beginning suddenly and intermittently?

The description of a condition that begins suddenly and intermittently aligns well with paroxysmal conditions. These types of conditions are characterized by episodes or attacks that come and go rather than being continuously present. The term "paroxysmal" itself often refers to sudden bursts of symptoms that can be severe but then may resolve spontaneously, making it the most suitable choice for this description.

In contrast, chronic pain is typically persistent and lasts for an extended period, while constant irritation indicates a continuous presence of symptoms without the intermittent nature described. Acute conditions, while they can start suddenly, do not typically capture the intermittent aspect. They are often defined by a short duration and severity but don't imply that symptoms frequently come and go. Thus, paroxysmal conditions best fit the specifics of the question.