to have reasons why you are not certain about whether sth is good or whether sth good will happen :
I've had my doubts about his work since he joined the firm.
It may be all right. Personally, I have my doubts.
to have reasons why you are not certain about whether sth is good or whether sth good will happen :
I've had my doubts about his work since he joined the firm.
It may be all right. Personally, I have my doubts.
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005