fitful
     adj 1: occurring in spells and often abruptly; "fitful bursts of
            energy"; "spasmodic rifle fire" [syn: {spasmodic}]
     2: intermittently stopping and starting; "fitful (or
        interrupted) sleep"; "off-and-on static" [syn: {interrupted},
         {off-and-on(a)}]
Source: WordNet® 2.0