Not sure what you mean by "automatically log on to each server that I connect to"? Do you actually mean other computers that log on to via ssh or some other means (I don't think Navigatrix does anything automagically in this case)? Or do you mean wifi networks?
In case you mean the latter: In the Manta Menu go to Preferenes >> Network Connections. This will open a window that looks like this:
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Under "Wifi", select on a connection that you don't automatically want to connect to and click on the 'Edit' button. This will get you the following (on tab "General"):
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Deselect the checkmark in front of "Automatically connect to this network when it is avauilable" and click on the 'Save' button. Repeat for all other connection that you don't want to connect to automatically. Alternatively, you can also delete those connections that you longer need.