This happens to me all the time and has for years. I mean I have taken naps with my head leaned against monitors at concerts, on trains, and on airplanes. 

Sometimes I will intentionally do this as a means to short circuit my brain when I can't settle down for sleep. 

I tried to Google what causes it and just got a bunch of stuff about toddlers. 

It's probably a sensory thing, figured it might be typical for this type of brain chemistry.