Recently I've noticed that, while switched off, my oven periodically switches on briefly. It doesn't ignite, but turns on the gas. I've witnessed it and it lasts about 10-12 seconds before turning itself off. I'm willing to replace the control board or thermostat or whatever myself, but how do I figure out which part is faulty?

It's a mid-90s GE model JGBS09PEF1WW. It's a basic gas range with electric ignition.

Thanks.