Funky sound after I lock my car
 

Hi! I have a 2015 A3 AWD. I have brought my car into the dealership numerous times and even shown the technician videos of the sound I'm hearing and I keep being told "don't worry about it it's nothing" or "we couldn't reproduce the sound." But I'm starting to get a bit nervous as my neighbor heard the sound while we were both getting out of our cars in the garage and he told me he had a similar issue with his Audi and it ended up being the actuator and the harness which led his car to be deemed "totaled" because it required a complete breakdown of the car? Keep in mind I know close to nothing about cars but know the sound I'm hearing it not normal. I'll take anyone's advice at this point:

- sound only occurs about 30 seconds after the car is turned off and locked
- sound happens 4-6x and then stops
- sounds like someone is jumping on a trampoline with rusty springs!
- sound comes from under the hood of the car

I can't upload a video here for some reason but I'd be happy to email it someone if they think they know what it is!!

Appreciate any input :)