2006 Ford Explorer jerky @ 40mph

Hey guys quick question as to what my be going on w/my 2006 ford explorer (auto/v6). Been running great until recently… Seems like when I am at a cruising speed of upper 30’s low 40’s and have my rpm’s at or below 1500 and my foot barely on the accelerator it shimmies and kind of jerks until I A)either accelerate or B)drop the automatic shift down into 3rd gear.

It doesn’t seem to do it if the cruise control is engaged.

Thanks for any help that anyone out there can give!
Jeremy