Only last about 5 to ten seconds then it smooths out. Runs great drives great. Intermitent check engines light on and off. Sometimes flashing sometimes solid. And it i
Only does it when the engine is cold

The flashing MIL indicates only one thing, a serious misfire, so you need to pull codes before chasing anything else. The two most common causes of a dead miss on startup that quickly disappears are a leaky injector or a leaky head gasket. Both will usually give you a small white cloud on startup because both are causing a cylinder to flood, one with fuel and the other with coolant. Once the flooding is expelled the engine steadies out.