Milky Oil Filler Cap

I changed the oil on my 1997 Jetta 2.0L the other day and when I removed the oil filler cap I noticed a milky residue on the bottom of the cap and a bit more in the valve cover. Is this the start of a Head Gasket leaking or something more serious? There does not seem to be a reduction of coolant as the reservoir is in the normal range. I would appreciate any help or experience with this issue. The car has 132,000 miles

Thanks

Not to worry. It usually is just moisture that builds up that hasn't had a chance to burn off (ie. cold weather driving or many short tirps).