It heated up for about an hour first

I suspect a door lock problem or a loose wire somewhere, like a loose ground wire. This can be in the breaker box, where it enters the oven, or several places in the stove. Here are some manuals: https://dl.dropboxusercontent.com/u/...aning_oven.pdf
https://dl.dropboxusercontent.com/u/...lure_Codes.pdf
https://dl.dropboxusercontent.com/u/...ning-ovens.pdf
I hope this helps. Look at all the wires, even in the receptacle on the wall. Loose wires cause fires, so you want to open the breaker box and tighten all the wires on grounding bars and on all breakers while you have it open. Use a screwdriver with a round insulated shaft as big as you can use without breaking something. If you find loose screws it indicates you also need to go throughout your house and check all receptacles. I have had wires burned several inches from receptacle and burned up light switches and receptacles from loose screws. Every time I have seen the problem you are describing it was due to loose wires.