Help me troubleshoot Cylinder 4 misfire

[mckbrew]

Symptoms

Check engine light with vsc lights.
Very brief rough idle on cold startup
sloshing sound behind dash

Code reader showed P0340

Pulled number 4 spark plug and looks good.
Also checked radiator for bubbles, inspected oil, etc as similar symptoms usually suggest head gasket issues. Nothing obvious here.

Any suggestions on where to go next?

 

[SUP3RJEFF]

What engine, V6 or V8?

 

[mckbrew]

6 cylinder.

This morning I started it up and had no issues. Last night so I was parked on a hill the other previous times I was parked on flat ground. Don't know if that made a difference. Maybe just pulling and resetting the spark plug was enough .