its because your engine is cold along with the oil. so the oil is thick and it takes a little longer before it goes through your motor. also in the cold, everything shrinks so the clearances aren't as tight as they would be when the engine is warm.
its usually pretty normal...
1997 BMW 540i/6 sport
1984 BMW 733i E23: Centra staggered 16" rims, Hartge strut brace, Hartge engine
1994 BMW 740i E32: Sold