99SL Knocking on cold days startup

[Carlos Serrano]

1999 SL 500.The car has 58,000 miles, last oil change at 57,000 miles Mobil1 full syntetic 0w40, OEM filter. the knocking only appears when the temperature is below 50F or abouts, it last for about 3 to 5 seconds and it goes away, it seems to be coming from the front driver side of the engine and can be hear above the normal sounds, air pump etc. after it goes away a ticking sound like a lifter can be hear for about 10 to 15 seconds and that one goes away too. I've tried to pinpoint the exact location of the knock but I'm not fast enough and can't get the wife to get up that early in the morning to turn the key for me. I am very concern about this and will appreciate any help, advise, you guys have help me a lot in the past and I thank you.