No heat in hotpoint

My 15 year old hotpoint dryer is working intermittently. The igniter coil goes on, but a buzzing noise starts at the same time. It lasts for a short while, then a click and the buzzing noise and igniter turn off simulataneously. I just want to know - Is it the coils? Is it the gas valve? This thing has pumped out 15 years. I’m afraid if I buy a new one, it will only last for 5. Please help.