Helping my dog overcome fear

Hello. Our dog recently became very fearful of something that we cannot control, and we're trying to find a way to help him. Any suggestion will be appreciated.

Our five year-old miniature Schnauzer has started this new behavior where he would get spooked and run to hide, seemingly out of nowhere, in our living room. Sometimes it happens when he's playing fetch, but he also does it when he's just walking. Afterwards he would avoid walking on that section of the floor, until a day or so after. This only happens in the living room.

We suspect that he is being extra sensitive after seeing/hearing fireworks around the New Year's Day (we happened to walk by our neighbors shooting fireworks. We wouldn't have taken him there had we known it.)

So far we are clueless as to what is causing this behavior. We checked his legs but he doesn't seem to have any pain. His nails look good, and no splinters, etc. on the floor that can hurt him. At times it seems like it's the creaking of the floor, or sound from the neighbors, or even our voice that set him off.

But whatever the cause of this is, I don't think it's anything that we can control. Last night it was particularly bad, and we tried to show him that there was nothing to be afraid of, but he wasn't having it, and was stressing out so we let him be. He eventually calmed down and went to sleep.

If it persists, we're going to take him to the vet, but otherwise, what can we do to help him overcome his fear? We don't overreact or baby him when it happens, but we also feel very bad that he can't relax in his own home. Is there anything we can do?

I would suggest just ignoring it for now. Let him go to a safe space and calm down. Then when he comes out, give him a fuss for calm behaviour. It's a sound rule when dealing with a dog, the less stress you show the less stress the dog will feel.