In Italian, if I say Indossano certe scarpe. (which Google Translate translates as “They wear certain shoes.”), I would be expressing a negative opinion about the shoes, for example that the shoes are inappropriate for the place, or they make appear ridiculous who is wearing them. That doesn’t happen with Certe volte sono triste. (“I sometimes am sad.”), though.
Can “certain” imply a negative opinion about something/somebody?
The equivalent in English would be “a certain sort of shoes”. This may be said with scorn, implying (without saying expressly) that the shoes are of a sort which is diagnostic of a vulgarity which one is too well-bred to name outright:
“Oh, my dear, her hat! her frock! and shoes” her voiced dropped dramatically, “of a certain sort!”
But that is not by any means the usual or even a common use of “a certain sort”. My impression is that is largely confined to fashionable circles of the first third or half of the 20th century; and since I was not of those circles I cannot say whether it was actually in use or merely imputed to them by novelists and playwrights.