I had a loose flexplate (flywheel in your vehicle) in my old 2001 Durango. Previous owner used a transmission shop staffed by idiots who didn't properly torque flexplate bolts (and the tranny filter bolt). One of 4 flexplate bolts had sheared off and the remaining 3 LOOSE bolts were badly scored. The holes in flexplate were also enlarged by the impacts.The odd semi-random noise the loose flexplate made, something like you described, stumped many mechanics. I suspected a bad torque converter and decided to start the repair myself. Once all the covers were removed the problem was obvious. Bushed the oversize holes, replaced bolts with new ones, threaded insert repair needed on sheared/missing bolt hole. Better option would have been to replace flexplate and torque converter but this was an ancient VERY RUSTY winter beater and I only wanted to get a couple more years out of it. The repair worked just fine for another 20,000 miles until something else killed the vehicle :-)
Plese, upload the video to Youtube and share it here so we can listen.