What is "by fits"

Fit \Fit\, n. [AS. fit strife, fight; of uncertain origin.

1. A stroke or blow. [Obs. or R.]

   Curse on that cross, quoth then the Sarazin, That keeps thy body from the bitter fit.
   --Spenser.

2. A sudden and violent attack of a disorder; a stroke of disease, as of epilepsy or apoplexy, which produces convulsions or unconsciousness; a convulsion; a paroxysm; hence, a period of exacerbation of a disease; in general, an attack of disease; as, a fit of sickness.

   And when the fit was on him, I did mark How he did shake.
   --Shak.

3. A mood of any kind which masters or possesses one for a time; a temporary, absorbing affection; a paroxysm; as, a fit of melancholy, of passion, or of laughter.

   All fits of pleasure we balanced by an equal degree of pain.
   --Swift.

   The English, however, were on this subject prone to fits of jealously.
   --Macaulay.

4. A passing humor; a caprice; a sudden and unusual effort, activity, or motion, followed by relaxation or inaction; an impulsive and irregular action.

   The fits of the season.
   --Shak.

5. A darting point; a sudden emission. [R.]

   A tongue of light, a fit of flame.
   --Coleridge.

   By fits, By fits and starts, by intervals of action and repose; impulsively and irregularly; intermittently.