My dog keeps wheezing periodically throughout the day, what's wrong?

Poor guy. He may have a type of bronchitis or asthma. I would definitely recommend getting him seen by your vet and get some x-rays of his chest done to determine the underlying problem there. I would also try video taping one of his episodes to show your vet so that we can get clarity on what you are seeing at home, since most pets won't repeat the event while at the vet.

Another possible thing this could be is a reverse sneeze. Look up reverse sneezing dogs on youtube to see if this is what Toby is doing. If he is having reverse sneezing episodes, then these are not of concern and are not life threatening. They are typically caused by mild allergies or irritation to the larynx. You can help Toby during these episodes by gently rubbing on his throat and offering him small amounts of water on your finger. If they become more frequent and start to impede on his quality of life, then you should visit your vet to rule out other undelrying causes that may require treatment.

I hope that things work out for your pet Toby moving forward and hopefully these wheezing episodes are just normal reverse sneezing events. Take care!