I have seen some fluorescent tubes in years past running in stores where there were stripes or rings moving up or down the tube.

I noticed this recently with fixture with two Phillips Alto T8 tubes in it when first on. Are those EOL or just need to be warmed up a bit? Do those eco style tubes that more often that regular versions due to lower mercury content?

Most tubes Ive seen doing it were the ones operated after long time inactivity and at a place that has been cold for a long time. And doing it only after start and only few times.
To me it looks like it happens after the mercury has chance to condense or get absorbed (into amalgams). What exact mechanism causes the effect I don't know, but it is most likely linked to the mercury vapor content or maybe its uniformity along the tube until it gets recovered into sufficient and uniform mercury pressure along the tube.
Or it could be some other gasses leaking in and needed to be hammered back into the structures to clean the tube atmosphere back...

Ah, that makes sense, as the one I had seen doing this most recently probably hadn’t been used in a while.