Silverstar could be onto to something. Could be a symptom of something though. E.g low blood pressure , which also ties to hypoxia - lack of white cells carrying o2 to brain also ties with iron deficiency- so get a blood test and check your red and white cells. You mentioned drowsiness, is this larthargy as low iron or b12 so could be anaemia. Wouldn't worry too much till you no for sure though huni. Yet if after food, monitor what foods as could be intolerant this day and age. X
No, it's not a symptom. It could be your blood sugar. I'd talk to your Dr.
No I don't think that it is a symptom. But like Silverstar said you may want to talk to your doctor and tell him whats been happening.