The feeling of mental inertia - the difficulty in starting a task and the ease of continuing it once begun - is so similar to the phenomenon of physical inertia, that one wonders whether, somehow, deep in the brain, mental inertia simply is physical inertia.
One wonders this even though mental inertia is easy to account for from thought based causes: clearing distractions, gathering facts, ordering work, segmenting concepts. All of that beginning-work is harder than execution, even when execution is drudgery.
