try this:

Make a sphere, called nurbsSphere1

enter the following expression:


if (noise(frame) > 0.5)
{
setAttr "nurbsSphere1.visibility" 1;
}
else
{
setAttr "nurbsSphere1.visibility" 0;
}



the 0.5 value represents the frequency of blinking.
Values between 0 and 1.
0.9 very intermitently on.
0.1 very intintermitently 0ff


Note :

if you want light to stay on for a few frames then its a bit more tricky.