actually ashwaganda does the same thing, it makes me feel wired. So I avoided for that reason. I have never done suma however so I don't know about that
The only reason I can think of that you would have a stimulatory effect would be an allergic reaction to the herb. This would cause a release of epinephrine in an attempt to counter the allergic response and would cause the stimulation. Otherwise the ashwagandha should be relaxing since it stimulates the GABA receptors in the brain, which has a calming effect.