Weird artifacts in translucent objects

Hi everyone,

I'm getting weird artifacts in my translucent shape and I'm not sure why. The one on the right was done by manipulating a circle and there are weird lines in the concave part of the shape. I made the shape using another circle and got the same thing so I used the Curvature tool to create the shape (left image) and there were less artifacts but there were still some. It looks fine as an opaque image but when the transparency was brought down, the weird artifacts become visible. Does anyone know why this is happening or what I can do to get rid of them?

Thanks!