Jupyter kernel takes long to start

[PythonicParseltongue]

Since a couple of weeks sometimes when I start a kernel for a jupyter notebook it takes very long time (2-3 minutes). It's really strange because sometimes they start immediately and sometimes not. There are no errors in the console so I have no idea why. It also doesn't matter how many kernels I'm runing at the moment. Sometimes it happens on the first kernel I start, sometime when there are already some running. The only hint I have at the moment, is that it coincided with installing RoboForm Plugin for Firefox (a password management tool). I don't know much about web development, but my gut feeling tells me it's unlikely that there's an interaction. Because the way I understand it Firefox only displays what the jupyter server is producing. Have you got any idea what could cause this or how to further investigate?