Recently on my MY 02 320, I noticed some small tapping sound that I believe comes from the engine compartment. It’s not a metallic sound, rather like some kind of rotary thing hitting a plastic part. It is more pronounced after a cold start, but also detectable with a hot engine. It seems only happening when the truck stops at a light or so. Because it is so subtle, I can’t tell if it happens at freeway speed. What could it be?

The only thing happened prior to this is that I changed oil and put a little bit more(right oil height when cold), so the dash shows Oil High when the engine is hot. I Topsidered some oil out after about 1000 miles and I don’t think it is the cause, is it?