Burner heating without cooktop being switched on

I have a 2006 Kenmore Elite electric cook top that was installed by the previous home owner when this house was built. This morning I noticed that the lower right burner was warm. None of the other burners were warm. The indicator light and knob were off. There was no noise. The unit is wired into the house, so I shut the breaker off. Does anyone have an idea what happened? I last used the stove three days ago. I have only ever had a problem with the upper left burner. If it was turned on, a buzzing could be heard off and on from the knob. I just don’t use that burner. I have had no other issues since living here.
Thank you in advance.

Nvreds, with the power supply turned off, the wires going to the element would need to be tested for continuity to ground. If none of them have continuity, the failure is in the infinite switch. Frigidaire 318191000 Switch (AP2129274) - AppliancePartsPros.com