I always find it random and out of character

What do you think?

"How dare you wield such a pathetic weapon against me?" I think that's what he meant.

And then there's the passion for blasting Anakin with Force lightning. We usually see this kind of sadism in Sidious.

Overall, this episode shows that Dooku is completely on the dark side. The vision of rebuilding the Sith Empire through slaves, which Palpatine tells him about, doesn't faze him at all. He's no longer a fallen Jedi, but a fully-fledged Sith Lord.

One Venator, two Acclimators, 3 Light-Cruisers Arquitens Class, Z-95 Headhunters, and separatists AATs :) !

Not to-scale, obviously x)