Second fermentation after 7 weeks

I brewed 10 gallon of a porter on Dec. 30. I've since kegged and am drinking the first 5 gallon of it and it is great. The second 5 gallon is still in the primary and it started fermenting again about 4 days ago. I've never opend the primary, not even to check sg. It again has a krausen and a whif from the airlock smells great.

I guess I should check the fg and if it's where I want it is there a problem with kegging it while it's fermenting? Of course I'll taste it first, but there's no visual signs of an infection.

Did you move the Carboy around, maybe rousing the yeast?

I moved it from the floor to on top of a counter about 2 weeks ago since I was planning on kegging it, but never got around to it.

Maybe that did have something to do with it. I suppose it's probably a couple degrees warmer on the counter than on the cement floor.