Yep, probly a good idea to hold out for warm weather before negotiating diagnosis with diesel engine. The happiest of my 240D's seems to bubble and pop at warm idle in summertime, yet naturally feels rougher in winter.

And that's true - being normally asphixiated self-combusting engines each must be treated on individual case scenario basis. Still I'd jump all over an IP timing adjustment, given the mileage.... not quite at replacing the timing chain, but close.