Check that 'Burnproof', 'JustLink' or whatever buffer-underrun mechanism is enabled. This includes a 2/4/8MB hardware buffer.
In Nero, somewhere, you can also set a (software) buffer-size during burning.
If either buffer does not get data quick enough, the burner has to wait for the buffer to fill up, before it continues. Nero counts these 'waits' and reports them.
You need to dig in the Nero-settings to bring this number down.