Does it smell like oil burning? I have seen engines so badly in need of valve stem seals and/or guides that they blow thick white smoke rather than just a puff of blue smoke. At other times does it blow any blue smoke? I would also consider oil (or similar) from another source as a possibility (eg. faulty transmission vacuum modulator or faulty brake master cylinder/servo).
107.023: 350SLC, 3-speed auto, icon gold, parchment MBtex (sold 2012 after 29 years ownership).
107.026: 500SLC, 4-speed auto, thistle green, green velour.
124.090: 300TE, 4-speed auto, arctic white, cream-beige MBtex.
201.028: 190E 2.3 Sportline, 5-speed manual, arctic white, blue leather.
201.028: 190E 2.3, 4-speed auto, blue-black, grey MBtex.
201.034: 190E 2.3-16, 5-speed manual, blue-black, black leather.