Isn't it enough to just ask, instead of to ask a question?
Which one should be preferable?
"ask" in this particular context is transitive. So it takes an object.
"I ask a question."
ask would be intransitive when you say to (someone) that you want them to do or give something.
"Don't be afraid to ask for advice"
For more, see Oxford Dictionary
If you say
people will realize you asked a question, but they will wonder About what? and certainly when one is asking about something one is posing a question.
Ask for permission
Ask for advice
Ask for someone's hand in marriage
In situations like those, the secondary effects are what people are interested in. For example,
P1: Was he asking for directions?
P2: No, just asking a question.
So it is not necessarily redundant to say
I asked a question.
but there is usually additional context which gets added
I asked a question about...