Idle has a "roll"

[mcgoo422000]

I have a 99 350 with 453,000. I don't cut it off much when I'm on the road.
It has taken a slight roll at idle now. The idle will vary 50-100 rpms by gauge not continuously but regularly. I was thinking maybe winter blend fuel?
The running otherwise seems ok. No check engine light on yet. Just wondering out loud should I start heading back home, I'm a thousand miles away right now.