It depends on the effect you want, here is an example :
Basically I have a curve that goes from 0 to 1 over 5 sec. This value is randomized but since it happens each frame there is the interp node to smooth it out. The values on the random node could be min 0.9 and max 1.1 for example, it would deviate the timeline curve by 10 %.
There are also these nodes “perlin noise 1d” and “pulsating value” that you can play with.
Playing with theses nodes, values and the curve shape you can have many random behaviors.