sono quasi morto di freddo
sono quasi morto dal freddo
Can anyone explain what preposition I should prefer in the above sentence?
And, always in reference to above sentences, supposing they are interchangeable there, can anyone explain why they are not in cases below.
sono quasi morto di morbillo
sono quasi morto dal morbillo
The difference is quite subtle. When you use "dal" actually you are meaning "dal troppo" ("because of too much").
For example, "sono quasi morto dal freddo" means "sono quasi morto dal [troppo] freddo" (I almost died because of too much cold), while "sono quasi morto di freddo" simply means "I almost died because of the cold". The meaning therefore is almost identical.
This is the reason why you can say "sono quasi morto dal freddo" but you can't say "sono quasi morto dal morbillo" since "too much measles" is meaningless: you just have or not have measles.
As Domenico already said dal is a shorthand for dal troppo and it always describe a causal relationship. di can provide a causal relationship but it does not have to.
For example, La Stampa uses Sensazione di troppo caldo o freddo (feeling of too much heat or cold). Here you can not use dal, as in sensazione dal caldo or sensazione dal troppo caldo, because there is no causal relationship. It's a specification about the kind of feeling.
