Sometimes, my KDE starts without the "taskbar"

@fell @linux

>Taskbar

It's the Plasma Panel.

>NVIDIA proprietary drivers

It IS possible that this is the core of the problem, as historically NV has been a major PITA for Linux, especially #KDEPlasma #Wayland. Lately, i've read many peeps mentioning large improvements, but afaik it might still depend on your specific GPU HW model & driver version. I don't use NV, so cannot help directly on that, but i have some suggestions:

1. If your current Plasma session is Wayland, try logging in an X11 session. Or, vice versa.

2. It might be corruption of a KDE/Plasma config file. A quick easy initial test is to create a 2nd user account in Plasma, then log into that.

3. If that behaves correctly, it increases the probability of corruption [of your original user]. You can reset to default all those, via the following:

To backup existing plasma config:

cd ~/.config
for j in plasma*; do mv -- "$j" "${j%}.bak"; done

This command will rename all Plasma related configuration files to *.bak (e.g. plasmarc.bak) of your user and when you will relogin into Plasma, you will have the default settings back. To undo that action, remove the .bak file extension. If you already have *.bak files, rename, move, or delete them first.

To backup existing cache:

mv ~/.config/Trolltech.conf ~/.config/Trolltech.conf.bak
mv ~/.cache/ ~/cache.bak
mkdir ~/.cache
kbuildsycoca5 --noincremental && kbuildsycoca4 --noincremental

Good luck.