Have this car seen frequent oil changes? You are using the right oil, but you need to change it often enough to prevent any sludging which would be the likely cause of your problem.

In EXTREME cold, like 10 degrees F or colder, you will get a slight amount of valve noise for a few seconds after start up. Hearing such noise in warm weather is alarming.

If it were mine, I would get it to operating temperature, which usually requires about 17 to 20 miles of driving and put a drain pan under it as soon as it is shut off and drain the oil overnight. With the oil you are using this will get the most sludge out of the engine that is possible. Continue to do this about every 500 to 1,000 miles for a few cycles and see if it goes away. If it does, go to a reasonable oil change interval and always drain it while the engine is at operating temperature.

Draining oil from a cold engine leaves the sludgiest stuff clinging everywhere. Draining it hot gets the crud out much better since it is churned up in the oil.