I could understand that if the new rotor was the only one doing this, but it's also happening with the old rotor which had zero problems until I swapped them out yesterday,

Brake pad sensor. I once installed it wrong way and it use to come in contact with something at every turn making grinding noise.
Could not figure it out till i took for other repair at indy and asked him to check it out. He put it right and all is well since.
Last sentence is wrong as car is on jack waiting for new brake fluid as i mistakenly removed caliper half bolt and lost some fluid in rear and have mushy brakes.

Some people(me) never learn to do it right everytime.

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1) '04 S500 Gold/Beige......120k Miles
2) '93 300E 2.8...Green/Tan MBTex..........202k Miles(and going)
3) '89 420SEL...Light Blue/gray Leather....155k Miles (Retired )

I guess I didn't make this clear at first, but I removed the caliper as one unit. Didn't detach anything, didn't remove pads, just slipped it off and back on again.

Did this for both sides.

Now it makes noise under tight turning, as in cul de sac turning, but that's it.

I think I'm just going to deal with it for now.

The W124 floating calipers have a cover for the brake pad sensors. Not sure if your E320 has the same type, but it's good to check if these are firmly clipped to the caliper and not dangling around (and potentially rubbing against the inside of the wheel).

Are the brake hoses or sensor/ABS wires correctly placed so they do not rub?

I just did the brakes on my 190E, similar car & brake design, with all new pads. Kept the rotors and calipers in place. I could see that the brake hose can become twisted when the calipers are removed and reinstalled.

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The E320 has 4-piston calipers, unlike the early w124's with front floating calipers. The clips are in place with the wires to the wear sensors tucked underneath.

Yep everything it in the proper place, and nothing was removed other than the caliper.

It is definitely a rotor rubbing against something. I wish I had a go-pro now!

I'm going to try pads next and see. Can you see my confusion?!

I have another interesting development...

I recently replaced my LCA's and ended up having a ball joint fail less than 5 months later. It does the ol turn-n-pop that all of them do when they fail.

Anyway I've noticed that once it pops that the noise clears up a bit until I center the wheel again. Still a rotor noise but this might be a contributing factor.

rotor rubbing sound should be constant as they are bolted tight between the hub and wheel.

intermittent can only be caused if the rotor is flopping around, which means the wheel bearing is really loose.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)