I bought this used (in excellent condition)as a one-owner car). I love it. Recently I have noticed a lugging or rattle when starting out in first or reverse. Could it be the motor mounts, the transmissions, don’t look???
You could try to step up the gasoline octane one grade. Also, look at a spark plug. It may show a black coating from running overly rich or burning oil.
There could easily be something loose, such as a heat shield on the exhaust system.