Oven slow to heat up

The last 2 times I used the oven, I turned the oven to bake on 350 degrees and the oven took about 5 minutes for the burner to go on. Both times there was a slight but definite smell of gas. After the burner went on, the oven worked fine and the gas odor disappeared. I am prepared to call a stove repairman, but am wondering if I can do anything to fix it.