Is my preamp dying a slow painful death?

My British Fidelity A3 (solid state) preamp is about 12 years old. It now needs about five minutes to warm up before making music. At powerup, there is a noticeable buzz from the speakers that cycles around five seconds of noise, five seconds of silence, which after a minute or two turns into five seconds of music (if a source is playing) and then five seconds of silence. Everything is fine after about five minutes. What is happening? Is this the beginning of the end?