Great advise Renee750il, I agree keep socializing the pup and don't coddle the pup when it shows fear. Just keep confident and praise the pup for walking past and object like the brave pup he is.
Fear of unidentified objects is an instinct that helped all animals including humans survive throughout the ages. It is called the "Fight or Flight" reaction. If it looks scary then it can possibly hurt or kill me, so for some pups/dogs they would rather flee and some would stay to fight...any cornered dog will have to fight.
When I first brought home each of my Newf's they each had a new item they had a fear of at first. One Newf would not walk across ceramic flooring (slip and fall fear), one almost died of fright when I picked up a bag of dog food and put it over my shoulder, he had never seen such a thing before and it scared the heck out of him. The dogs were never abused, they just never saw these items and reacted in fear.
So as Renee750il mentioned, keep socializing your pup, treat and praise when the pup ignores or braves a new item. Sometimes with new puppies I'll put an item on the floor and let them explore it themselves, I just sit back and relax so they don't pick up any anxiousness or nervousness from me.
Next time you are out walking and a trash bag or something else flies across the path..just keep going...most pups/dogs will react by looking at it, hunching their back and backing away from the item...but given time they will go up and explore it once they realize its not going to eat them.
Think of how you would feel if you were walking along and a big organic bubble rolls in front of your path...hey, it could be harbouring aliens for all you know
You too would stop, perhaps back away...maybe even run from it...then curiousity would get the best of you once it showed it wasn't coming after you and you would explore...don't expect your pup to react any better. This is why socializing a pup to many different things in a positive manner is so important before the age of 16 weeks. A pup that is socialized properly is more confident and better able to take cues from their owner that the new items are not going to eat them.