1995 740il Radio Problem

[Pe!pe!]

I have read a few postings on problems associated with the radio on ealier E38s. My problem just started, the sound on my radio does not come on until a few minutes after starting the car. Sometimes it seems that if I accelerate the car the sound comes on quicker. This problem is only on the radio and cassette feature, the sound from the cd changer is just fine, even at start up. Any Ideas of what is going on? Thank you