Die-off manifests as a short, harsh general all-body reaction, which may or may not include multiple symptoms like facial or body flushing, headaches, dizziness, weakness, fatigue, abnormally high energy, headrushes, sweating, nausea... And then goes away. Quickly. Probably within the hour.
Not sure if they're a sign of things gone bad, but damn sure they do happen with azoles, are in fact a side effect, and have schit-all to do with die-off. Been there, done that, still wearing the t-shirt. Got one of 'em nasty headaches as we speak. Thoroughly enjoyable :(