RPM is jumping up and down when engine cold

I have a k12 1.2 micra and for some reason the rpm is jumping up and down when the engine is cold but after a few miles the issue seems to go away and if i leave it for an hour or so it comes back till the engine gets warm i have the check engine light on and a p0300 multiple cylinder misfire code. Any ideas what could be the main issue there are plenty of causatives hope you can help me with it.
 
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