IVIG side effect

I have been receiving IVIG every ten days 25 gms. On the day after the infusion and 3-4 days afterwards, I feel that my legs are sort of “weak” when I go for walk. I feel that I cannot walk as fast, but I don’t feel any pain. I don’t know how to describe it. Later on, my legs feel better. I read that one of the side effects of IVIG (Privigen) is “asthenia”. Isn’t this side effect counter intuitive from what we should expect from IVIG to help with the CIDP? Does anyone experience this?