I read a post I think from sassy. She seems to have "hit the nail on the head". My energy drops instantly. I need to put my head down and let it get through me. It lasts only about 2 minutes then very slowly my energy comes back. Maybe another 3 or 4 minutes. After this I feel good and ready to do anything I want. These episodes come a few times during the day mostly before noon. They do not happen when I am walking. I have had this issue for the past 7 years. I asked my Cardiologist and he told me he did not know the cause but did not think it was heart related. I have also asked 2 other Drs. and they had no idea what causes this. One other thing. This problem used to go away for months. Then come again for 2 to 3 weeks and gone again. Now it will not go away.