Just flew ORD->CDG (UA942) this morning
Sitting on row 19, window seat (i.e. not very far from CoG), I noticed (1hr into CDG, FL360 or 370) that the leading edge seemed to be slightly and slowly oscillating wrt the horizon (line of sight = 45 degrees from roll axis, period=some seconds). I looked at the wingtip but I did not see any visible roll. No turbulence at that time and I did not feel any movement (as a glider pilot, I tend to think that my portable motion indicator - i.e. seat of the pants - is more sensitive than the average SLF's one)
Was it some effect of the yaw damper ?
Or was it just the effect of sleep deprivation because of the cattle class night
edited (many times) for clarity & spelling