My car misfire's at low rpm and only in the morning or when the car is very cold, what can it be?

It could be as simple as water in your gas

But only when its cold and on low rpm, from 2000rpm and up it revs clean and idles right and when its temp starts picking up the misfire is gone?

what do you mean by misfire? engine shakes more than usual?

The engine doesn't rev clean, it struggles to rev up til it hits 2000rpm and then it revs clean. Basically the engine runs un even and not properly.

check replace ECM temp sensor.

Possibly an ignition control module failing on the low RPM side u can test that at a local parts house

wow, is it really 344k miles? engine could just be too worn out maybe a compression test is in order?