Do you doubt, because you are afraid .. Or you are afraid because you doubt?
As others have said better than I can ... this is a false dichotomy that suggests everyone both fears and doubts, and then simply questioning the direction of an assumed causal arrow between them.
In point of fact justifiable doubts are healthy things and not to be feared by rational thinkers, nor are they cased by fear. Justified doubts are caused by a lack of valid evidence to substantiate the thing doubted.
Quite the opposite. Fear seeks to eliminate all doubt, and the meek, out of fear, avoid troubling questions that might cause one to doubt. Fear is one of religion's most effective tools against doubt.
Neither. I doubt things until I have evidence to the contrary. I have no fear of doubt whatsoever. When I see an advert making claims about a product I have a healthy scepticism until I find evidence to back up the claims.
And I an certainly not afraid of doubt.
If you are referring to a god claim, then I have no doubt and no fear. There is insufficient evidence that any of the gods desribed by the various religions do. or can, exist. No doubt. No fear.