I got some hawthorn berry pills the other year, and when I took them, I noticed that I got really tired, and could hardly move (for hours). I didn't particularly mind this when I wanted to sleep, but it was troubling, since I didn't know why it had this side-effect, and I was worried it might kill me or something. Just to be safe, I stopped taking it after a few times.

Has anyone else had a similar experience? Any idea why this side-effect would happen?

I know it's supposed to do something for your heart.