A practitioner falls asleep in sitting meditation when, in fact, already
fatigue-stricken earlier in repeating the Buddha' s name. Fatigue intensifies
if losing concentration and hence makes one all the sleepier.
It is a matter of course. There is no need to feel confounded. Go for a
physical checkup, maybe, to find out what' s wrong. Pay attention to
diet. Rest well. Make changes to ensure that things will get better.