Louder than usual engine sounds between 0-30 mph

I have a 2006 Hyundai Elantra that is sounding louder (like I am flooring it - just for few seconds) than usual between 0-30 mph. After that it seems to level off and runs fine at about 60 mph. The engine light isn’t on and the pick up seems fine. Is this normal? I don’t want to spend $50 for a diagnostic for nothing but I also don’t want to drive around a car that needs repairs. It’s only got 40k miles on it so it seems strange that it would have issues already. Also, I am good about regular maintenance etc. Anyone got any ideas?

Does this car have the Hyundai 100k mile Powertrain Warranty?

If so, I suggest taking it to the dealer for diagnosis, as it sounds like you are experiencing transmission slippage. If that is the case, it will only get worse, so why not have it checked out sooner, rather than later?