Initialize signal with random number

Is this part of a test bench or a synthesizable design? The uniform function is most probably not synthesizable. I think the only way to use it is to put it in a process and initialize your signal from there. The Uniform call modifies the seeds, so it can't just be used as an initialization constant.

What exactly are you trying to achieve? Even in a test bench, if your seed values are initialized with a constant value, the Uniform call will return you the exact same sequence of "random" number at each run.