Hazards blink after a few minutes of truck being off.

[shotgunfatcat]

I did some google searching and a bit of searching on here, so forgive me if I missed it, or it is a common thing, my last Chevy was an 07. After I get out of my truck and a few minutes go by the hazards flash a few times. The only thing I can think of is if it is some kind of warning for not locking the truck? The times I have noticed it happen I don't think I locked it. Or is it something else I should know about? 

[EddDe]

I have a 2020 1500 and I see tail lights flash when truck is shut off and fishing boat trailer is attached. Dealership says this is normal, but I didn't have trailer theft active. I found TSB 20-NA-198 that applies to 2019 & 2020 models that I'll ask about at next oil change.