I turned on the dryer and it ran for about thirty seconds before it just stopped. I pushed the start button again, but it wouldn't start at all.

Is the motor trying to start? Is there power to its outlet?If it is gas try plugging something else into the outlet to check for power. If it is electric turn the breaker off for ten minutes then turn breaker back on again and try the machine. If you have a volt meter you could check the outlet for power that way. If the motor is running when you push start but the drum isn't turning than you probably have a broken belt. Is the door all the way shut? If so you could have a broken switch at the door. To check the switch would require opening the machine case and using an ohm meter to check the switch. The last thing it might be is the timer. If it is an older (ten or more) unit and it is the timer then it might make more dollars and sense to get a new machine.