Smooth the low-poly cylinder 

Cylindrical mesh made with low polyAdd polygon division toHow to make the mesh smootherIntroducing 

Assume a cylindrical shape with conspicuous jerking as shown below. 

Select the edge of the end of the cylinder. 

Edge→Subdivide Edge-RingChoose. 

You can enter numerical values such as the number of divisions at the bottom left of the Viewport. 

I increased the number of divisions to get a smoother cylindrical shape.