short buzzing noise when I drive off

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'02 Mazda Protege5
I hear a 1-second buzzing noise from under the hood every time I first start the car and drive off. like when once I start moving I hear it and then I don't hear it again the rest of the drive. I would have disregarded is as a normal noise but It only recently started happening. I'm thinking there's a valve or something that is about to fail. Any ideas on what it could be? This is all the info I have to go on right now lol.
 
my old Capella had this issue as well. It also happened under hard engine braking. I never got to the bottom of it but nothing fell off/ went wrong. Apparently it can be the starter motor not retracting properly, try replacing the starter perhaps?
 
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