I used to have this happen to me. Mine lasted several minutes tho. I learned that my B12 was going low certain times of the day. My doctor recommended that I take B-12 vitamins to see if that would help and to ALWAYS carry around some time of food with me, ie crackers or energy bar or whatnot...so that if this should happen, i could eat something and get pepped up. Ive been on the B12 for 3 months now and havent had another episode..i still carry some food with me just incase.
I suggest you talk to you doctor about this. It may be different with you.
Good luck,
Rhea