Hi @papa_sangre
It sounds to me like you either have a loose connection between Bela and the accelerometer, probably near or at the accelerometer, or the accelerometer itself is broken leaving that connection floating. Bela's analog inputs have extremely high impedance, which is generally useful in a lot of ways, but when unconnected they react quite dramatically to charges in their vicinity - try scoping the unconnected analog inputs whilst poking your fingers near the input pins, both with and without your hand grounded on a laptop or similar.
If the accelerometer itself or your connection to it is broken, your cable will be floating, and if it is two metres long it will make a fantastic antenna, picking up electromagnetic fluctuations in the air. Do the oscillations on that channel happen to be around 50/60Hz (or double that at 100/120Hz)? You can check using the FFT mode of the Bela scope. If so it is probably picking up signals from the mains wiring in your room. The reaction to your rubber shoes is probably something to do with static build up.
So I would double-check the wiring around the accelerometer, and if you can't see anything wrong try replacing it, or at least looking at the outputs on a standalone oscilloscope to check it's working.