Car gets mad if abandoned for one day

Hello, newbie here. My 1998 car has developed a temper these two months. If not driven for over a day, the engines gets jerky once started and it becomes very hard to accelerate. Usually it takes 20 min for the gas pad to normalize. Also may be unrelated, an odor like natural gas is easily detected after the car is parked. Maybe it’s an exhaust problem or the two are unrelated? Many thanks!

Has the car been overheated recently? Hows the coolant level?

You haven’t supplied enough symptoms to guess at a cause. How difficult is it to start the engine? What is un-normal about how the car performs for the first 20 minuets?
As a first guess, the fuel pressure may be off. Measure fuel pressure at idle, at 2000 rpm in DRIVE, and 5+ minuets after engine shutdown. Results?

no. coolant level okay.

Thanks for the reply. Not hard to start the engine, but with the engine started after 1 or 2 days of rest, the rpm goes up and down for a while before stablizing. Need to floor the gas to get the car to move forward and gradually the symptoms dissolve. I have not checked fuel pressure yet.