Obviously wwwaaayyy too little info to suggest much however you seem to be saying Upper left Quadrant 'fluttering/Spasming' with no associated pain.
First two things that come to mind are diaphragmatic irritation, which is often blamed for hicups and symptoms like yours. Just like with hicups it usually passes and causes no trouble at all.
Are you under a lot more stress than normal with your huge recent workload? Cos it could also be a form of nervous twitch caused by stress, most people get the fluttering in other muscles when highly tired or stressed like above the eye or 'in the stomach' but diaphragm is well within normal ranges too.
As I said though those may as well just be guesses. The only things in that area are Stomach, diaphragm, spleen and splendid flexure. The only ones of those capable of a fluttering sensation would be muscles around the stomach and the diaphragm.
Overall might seem wierd but doesn't sound overly bad, only worry if it keeps happening over several days.
