A slight modification of Laurent Roro's solution worked for me. I changed camera Clip End first, but the flickering remained the same. I then changed camera Clip Start, and the flickering completely disappeared. My scene had objects from a little over 100 feet from the camera to 7 miles back, so the default (?) setting of just over zero for Clip Start apparently caused a lot of flickering on the distant objects.
Update: In reply to Ben's inquiry, while I don't have the scene in front of me right now for exact numeric values, I lowered the Clip End to a little beyond the farthest object. Like I said, that didn't really change anything for me. I just now opened Blender on my work machine, and I see that the camera defaults to a Clip Start of .328 feet. I'm guessing the reason mine started out far lower might be a result of importing the camera from After Effects. Anyhow, I changed Clip Start to 100 feet, since the nearest object was at 140 feet or so (can't recall). My reasoning was that it might be similar to the old shadow maps in Blender internal, but that's not a very scientific line of reasoning, or an explanation. Anyhow, the difference was dramatic. I had a particular, low roughness tower in the background that had been flickering like crazy, such that the entire tower basically changed shades of gray from frame to frame.