That’s a lifter and not normal for a low mileage truck. The lifter is for whatever reason taking a few seconds to pump back up which is why the noise goes away. Been around enough pushrod V8s to know that sound, and it’s not unique to Ram.
Just out of curiosity what oil and filter are you running? How many miles on the truck?
I have 13K on my ride, and it does it once in a blue moon. I talked with my SA and mechanic at Dealership (guy knows his stuff), said happens, kinda how the 5.7 and the 6.4 are at times. Normal, BUT he stated: Whatever U do, use good quality Oil and Good Proper Filter at all times. Running proper Mopar and 5W20 full synthetic on mine. IF I was doing a lot more harder stuff in summer here than just normal driving, ie., a lot of heavy towing etc.,. I would use 5W30 due to heat, but this is all IMHO.......
ADDED: OP, whatever U do, take all we say with a
Grain of Salt as we all have different experiences. U do
WHAT U THINK is right, and not what ne body says on an internet thread, regardless. Your Truck, Yer Wallet. I am happy with my ride, so I stay the course. Also OP, regardless, make sure truck goes to Dealership and have this ANNOTATED in records as a safeguard.
CAVEAT: RandomRam: I used to get that "sound" on old Chevy V8's, due to lifters and rods wearing and they were adjustable liters on drive train. But alas, that was a lot of Moons ago and engine design a lot different. I have more than once stood in the driveway, pulled valve covers and adjusted cause money was an issue, no money to replace, just saying.....BUT that prob not the case here, since all solids, MDS lifters, and such, but I have never opened up one of these beasts, just old 383's, 396's, 327's (showing my age).