ABS Light Comes On

Sometimes, while driving, ABS light comes on. If I shut-off the engine, and start again, it goes away for a while. When the light comes on, ABS does not kick in, speed is unchanged.

1995 Camry, LE, 4 Cylinder

What could be the problem? Big issue?

it can be a variety of things. take it to a mechanic and have them pull the ABS code