Ticking noise from back of truck

Vehicle listed above is a 2004. When I turn off the truck after a drive, there is a slow ticking noise. Slow like 3-4 seconds in between the ticks. The noise is coming from the back of the truck near the gas tank behind the wheel. I turned the truck on, let it run (without driving it), turn it off and it does not make the noise. Only after being driven does it tick. Once I turn the truck off, it makes the noise. When the truck is started, there is no ticking. I can’t hear it once I start driving either. The ticking sound lasts about 2 minutes after turning the truck off.