Hi there. Welcome to our site!
I’m a retired master technician and tech instructor with over 30 years experience. I also have access to a pretty good database on automotive service and repair. All of which enables me often times to offer you an educated guess on what the problem with your vehicle might be. However, if you’re thinking on working on the vehicle yourself, all my knowledge and resources won’t help you if you…
… don’t have tools or the skills to use them
… don’t know there will probably be some special tools and equipment needed for a proper diagnosis
… don’t realize it may take a few back and forth replies to solve the issue
… don’t understand that I will need you to provide specific information
Cold misfires mean the engine is not getting enough fuel. Since the problem clears up once the engine warms up, I would say the ECU is either not getting the proper signal from the coolant temperature sensor (could be caused by bad sensor or connector or wiring or air pocket in the cooling system) or the ECU itself is faulty (unable to interpret the signal it gets from the temp sensor or unable to increase injector-on time).
Do you know how to retrieve trouble codes from the ECU? If so, can you do that and share the results?