Tensorflow and random variables

one question about random variable. Let's suppose I need a random variable inside my loss function. In tensorflow tutorials I find random functions used for initialize variables, like weights that in a second time are modified by training process. In my case I need a random vector of floats (let's say 128 values), that follows a particular distribution (uniform or gaussian) but that can change each loss calculation. Defining this variable in my loss function, is the simple thing that I need to do, since at each epoch I get new values (that anyway follow the selected distribution) or I get the values that are always the same in all the iterations?

Thanks,

Daniele