Radio/tape Cd Player problems of the 2015 Hyundai Elantra

We have had problems with this car for years now. 2 of the issues the dealership could not even fix the problem. On 11/15/2016 with 12185 miles on the car, we had to replace the battery on the car. On 05/22/2017 with 15516 miles on the car, we had to replace (2) tires on the car because the tires were bald. On 11/03/2017 with 18268 on the car, we had to replace the other (2) tires on the car because the tires were bald. We had problem with the car stalling. The dealership could not find anything wrong with the car. On 01/18/2018 with 20747 miles on the car. We had a problem with a sound when the car starts. When the car starts it sounds like metal clinking. It does not matter if the car is cold in the morning or anytime of the day. When I start the car, it makes this sound. I had to tape the sound so the service advisor could hear the sound. The tech could not hear it. 02/08/2018 with 20749 miles on the car. We still had the problem with a sound when the car started. When the car starts it sounds like metal clinking. The dealership kept the car overnight. The next day the tech did hear the sound. They tested the alternator and it was bad. They had to replace the alternator on the car. After the dealership replaced the alternator I still had the same sound as before. The replacement of the alternator did not stop the sound. 03/20/2018 with 20802 miles on the car. We are still having the same sound when the car is started. It does not matter what time of the day the car is started, the same sound happens. It sounds like a metal clinking. I had a tape of the sound, the tech did not hear a thing. We are still having the same issue with the sound when the car starts. I am scared to start the car because the dealership can not find out what is wrong with it. I am scared it might blow up when the car starts because of this issue.