Stirred, not shaken!!!! Hobby paint bottles are too small to provide sufficient cavitation to adequately disperse the pigment and binder in the solvent.
If it disperses completely, it should still be fine. It may take a lot of stirring, though, if it's been sitting very long—up to ten minutes (less for Tamiya and Gunze, a little more for Polly Scale, longest for MM.) If there are strings of goo, it's dead, Jim.