That's really weird, Kaküno in my experience will start writing immediately. If it's having issues starting (ink not coming out), you can try squeezing the cartridge, or if you have the converter you can twist the knob and push some more ink through. Is the problem when you uncap the pen or only after you switch cartridges?

Edit: Or, the pen you have might just have a poor nib. Sometimes these things happen. T_T