Another vibration question

Hi all. New here. Recently grabbed an '05 AC V6 2wd (I know, but I liked the better gas mileage and don't really need the extra V8 power. It's mainly gonna haul mulch and tow a Scamp) with 98k on the clock, and no rust. Which is a big deal in MN (was a California truck).

The only issue it's having is what feels like a driveline vibration, usually when accelerating very gently, like when you're coming off a stoplight behind a slowpoke. Medium to aggressive acceleration doesn't produce the vibration. It's usually a pretty mild vibration, but it got a little more intense when the weather went from the 70's to the 30's.

Had it in for a transmission fluid exchange because I didn't know what was in there and wanted to make sure it was the Toyota fluid. While there, I had 'em check the driveline over. They said everything looked fine, and didn't feel a vibration, which makes me think they didn't accelerate gently like I told them to. Couldn't ride with the tech thanks to COVID. They couldn't grease the u-joints because the 2wd doesn't have zerks.

So, is this something I should be concerned about, and if so, what would you guys do to chase it down. I'm pretty comfortable working on cars, but the only other RWD vehicle I own is an MR2, so you work on it like a FWD. Not overly familiar with driveshaft/diff issues.

Thanks in advance.