Unfortunately there could be a dozen different reasons why a car feels off on any given day. Weather is certainly a factor, as many have mentioned, and probably the most easily forgotten one. There's also your air filter, fuel filter, or any other number of consumable things involved in your running process. You could get as many different answers as people you ask. My thoughts went to possibly getting a bad batch of fuel, which is always a possibility even from known brands that are supposed to be higher quality. And there's no remedy for that except to run through the tank and hope the next fill isn't the same or worse.
As long as it's not a gross loss of pep, I wouldn't sweat it or think the car's getting old already at 30k. Heck, @
Tcoat is in the six-figure mileage club and (I think?) still even on his original spark plugs.