Auto restart predictive dialing

if agents are available, the system will continue dialing the number of lines equal to the number of available agents as I understand it.

No, it will dial use all available lines. The reason is that for predictive mode, not all lines will reach live answers. The system always tries to get more calls to go out.

If you see a lot of dropped calls, you can either add more agent or slow down the dialing. You can do so under predictive dialing options.

If no agents are available, then it stops dialing. Will it automatically start dialing again if an agent signs on?

Yes.