Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
somnŭlentus (somnŏl-), a, um, adj. [somnus], full of sleep, i. e. sleepy, drowsy, dozy, somnolent (post-Aug.), App. M. 1 fin.; 10, p. 251, 37.
Hence, adv.: somnŏlen-ter, sleepily, Hier. in Psa. 118; Sol. 20, 7.