Question- secondary fermentation/spritz...

I've seen comments regarding the mention of a spritziness to a normally flat wine, perhaps caused by fermentation in the bottle.
I just encountered this on a 2005 Mas Carlot Les Enfants Terribles.
My original tasting notes:

An interesting blend from Costieres de Nimes consisting of 50% Mourvedre and 50% Syrah, quite nice value at $12.
Dark dense color, very drinkable now and right from popping the cork. Forward aromas of bright,tart cherry with that Mourvedre meatiness(if you know what I mean)and wood hints, very appealing. Again red fruit, mineral, woodsy flavors. Deep flavors, very lush texture. I feel the fruit and brightness faded after about 3 hours making a more brooding funky mix.This wine paired wonderfully with spicy Italian sausage grilled in peppers & onions,
with a pesto pasta side.

First bottle was great, second bottle was...different. Hard to explain, not bad but not great like the first more muted and it had a definite bubbly spritz.
Is this good, bad or indifferent?
Any comments or explanations are appreciated.
TIA

Hope I’m not confusing you Mike, the term “flat” is a negative term itself, usually a term used to describe a wine with no vinous character or lacking acid. A much better term to use is the term “still wine”, a wine without noticeable bubbles or CO2. Most all wines might have some CO2 dissolved in them, hopefully however in “still table wines” the “bubbles” or CO2 will not be so noticeable. Wines that are suppose to be “still table wines” and do show some “spritz”, and the wine is now “unpleasant” to drink, yes I would consider that a flaw. Yes this can be caused be a “renewed” fermentation or MLF (malolactic fermentation). But if the wine is still “pleasant” to drink you could try to pass it off as a “frizzante”

Salute

As Victor says. Usually, spritz in a wine that's supposed to be a still wine is considered a flaw. If it's not too pronounced, though, the wine can still be very drinkable. Sounds like yours wasn't so good.

Great responses, not confusing at all.
Thanks for your patience in helping me learn and understand.
Mike-