marc108 wrote:you could try walking or standing meditation, its unlikely you'll nod off doing that. nodding off after 30 mins of meditation is a good indicator, imo, that you're deeply fatigued. i think if your busy work schedule is interfering with your meditation theres no shame in putting off whatever volunteer work you are able to and having a little more free time, especially if you plan to use it doing skillful things like sitting or studying the Suttas.
if you have health insurance it would be wise for you to go to the doctor. get a checkup and some basic bloodwork. also vitamin D, iron, methylmalonic acid.
you could try taking a multivitamin & 1-2g of fishoil every day as well.
i'll also add that getting lots of sleep helps. as does meditating when you are very much refreshed. not after work or when you feel sleepy or worn out. by all means give it a shot whenever you get a chance as any meditation is good meditation. there's nothing wrong with sitting after work and getting up when you feel you can't stay awake any more, don't get frustrated. i have the exact same problem. being very rested works for me as does meditating outside in the fresh air.
you may sleep seven hours a night and feel rested but still doze during meditation when you really need 8 or 9 hours of sleep since your body is worn out. try different combinations but know there is such a thing as to much sleep.
also the words of the man himself on the subject may help you, this is a sutta where the buddha gives some suggestions to a sleepy maha moggallana:
http://www.accesstoinsight.org/tipitaka ... .than.html