Consistent 11 second Clicking in Vent when heat first turns on, not vent expansion?

I've experienced clicks or expansions in the ducts that make a noise before (almost every home I have had had that). But this one seems a bit different. It does happen right when the heat comes on - we hear it predominantly from one duct on the side of the house that goes to our bedroom (which is also closer to the HVAC unit). The noise starts low and then gets louder. It is only one "click" instead of multiple in succession. When it starts it's one click every 3-5 seconds. Then it slowly goes to every 11 seconds. It eventually stops - 5 minutes later perhaps.

Is this really just the ducts expanding? I ask because it's actually fairly annoying - more annoying than I have experienced in other homes.

I have a Bryant gas heater, and live in the Mountain West. I have had my ducts patched up a bit as the previous home owners did a shoddy job. Filter was just changed yesterday. Heating unit is getting up there in age but still operating fine.

I will post a video of this when my account allows it.

source https://hvac-talk.com/vbb/threads/2235298-Consistent-11-second-Clicking-in-Vent-when-heat-first-turns-on-not-vent-expansion?goto=newpost