(n.) an excessive desire to stay in bed
Clinomania is an excessive desire to stay in bed. (The definition of the word ‘excessive’ here is up to you.)
That word first emerged in the psychiatric literature of the late nineteenth century, with one article from 1890 identifying it as one of several “phases of sadness”, and defining clinomania as “the passion of staying in bed”. From there it fell into more widespread use in the mid 1900s (it made its debut in the American Illustrated Medical Dictionary in 1951), and has remained in albeit occasional use ever since.
Etymologically, the ‘clino–’ of clinomania comes from a Greek word various meaning to lean, slant, or recline. It’s not a particularly productive word root in English today, but it nevertheless crops up in a handful of undeniably useful words like clinopinacoid (“one of the three principal planes in the monoclinic system, running parallel to the vertical and inclined axes”, apparently) and clinoid (an adjective describing anything resembling a bed).