1995 Chevy Cavalier Hesitation

Engine problem
1995 Chevy Cavalier 4 cyl Front Wheel Drive Automatic 186000 Kilometers

Just today my car started running funny, when I first start it up the rpm's jump up and down until I give it some gas then it will stop, then when I go to take off it starts hesitating like its getting choked in which it has trouble picking up speed. Once the engine gets warmed up it will stop doing it. It has a new fuel pump, fuel filter,
thermostat, alternator and battery which were installed about 3 months ago and a couple of days ago I had a new muffler put on and some coolant tablets put in the reservoir to seal a little leak I had in the head gasket.

Edit

i was just out driving in it and it has gotten worse, it now makes a knocking noise when I am accelerating.