If the radio has a slide control for volume, it may be dirty. The band selector may be dirty, the tone control may even be dirty. These are things that rotating, or sliding the control through the range of travel may clear up for a little while, and it just means dirt, and often this is associated with a crackly sound as you move the controls. Another possiblility for the internal problem is a cold solder joint, and these are usually acompanied with a "pop" sound (but not always.), or the volume changes abruptly when an appliance motor starts, such as a refridgerator.
If the radio does it all the time, no matter where it is, it is likely internal, and if new and under warranty, perhaps getting it exchanged, otherwise if it does this in one area of the house, or cetain times of the day, or when certain appliances operate, the problem is external, and moving the radio is about all that you can do.
:Hi everyone, I recently purchased a Cambridge Sound Works Model 88 (Kloss) & while the reception is so much better than my old radio, the volume seems to go up & down. Does anyone have any idea what might be causing this? I know this is not an antique radio question, but I thought perhaps one of you uys might be able to help me out. Thanks