98 galant small/big problem

When i take off in my car when it is fairly cold out. When taking off in 1st gear i get this thing like the engine isnt turning over smoothly. Like its chugging along and that its like frozen. It does it for a while then stops when the car gets warm. I have tried using some engine flushers and i switched to a amsoil synthetic oil and that didnt help the problem. I dont know if its a big problem or a small problem. Also at an idle my car misses. It only does it when its warm and sitting in one spot. It will bob back and forth between 600-900 rpms. I replaced the plugs, wires, and i just bought a new distrib cap and rotor. I havnt put them on yet, but could it be anything else? Thanks. the car has about 108000 miles on it. 2.4 Liter I4 Cyl. Manual