bed mumbler

A person who speaks in a low and poorly articulated voice when sleepy or recently awoken, so that you have to constantly ask them to repeat themselves. Especially refers to people whom you're lying in bed with.

you: So we should do this again sometime babe.
bed mumbler: (incomprehensible rubbish)
you: What?
bed mumbler: (incomprehensible rubbish)
you: Wait, say that again.