Ours does this, particularly after being cleaned, where some water has got into the switches and is causing a short. Probably worth pulling the knobs off the switches and having a bit of a clean and it may go away...
Do you mean the button you press down to get the spark to light the gas? If so I'd suggest it's got glued up with crud and needs a good clean, so it can spring back properly.
I don't think it's the button that's causing the issue, but I'll check it. But yes, it's that noise which keeps happening when i'm not touching the button.
We had this recently and despite giving it a good clean, it continued to spark randomly. We were concerned about this happening whilst we were out and took the switch apart. In the end we replaced the ignition button on the hob and everything is back to normal. It cost us £12.
