runs rough when cold, runs better when warm

[Rag]

i purchased a 1990 240sx, 5speed, no rust.

i searched but found little to no info on the subject

like the title states it runs rough until engine warms up, then apparently once the engine get to operating temperature it evens out for the most part.

this is all according to the previous owner

steer me in the right direction

i want to say the coolant temperature sensor or o2 are culprits... id like some advice