Hi Maverick,
Two things come to mind.

1. When I was young and up until I had B12 replacement I would sort of black out if I stood up too quickly. Things went black. I didn't faint, it would clear up and I'd feel a bit dizzy for a little while. That was very frequent. It went away completely after I had B12 replacement. Prior to that doctors would say it was from low iron, and I would then be given iron which helped.

2. When I had tetanus a few years ago I would break out in a sweat when the seizures hit. I think it was because they are so scary.

If you decided to try Methylcobalamin, the active form of B12, then it might be good to also increase the potassium in your diet. B12 tends to help blood cells become normal, if your kind of low B12 affected blood cells. When blood cells begin dividing normally again they use a lot of potassium. If you're low in potassium the increase in need, that can't be met, can cause muscle spasms and a sense of weakness, if not actual weakness.