Q.Topping or Pruning an Oak Tree
I have an oak tree that is approximately 8 years old now. It stands about 15 feet tall but the top 4 feet of it is branches are shooting up about 4 or 5 of them. My question is when is the best time to cut these off?

Oh boy. Pruning a young tree correctly is very important to its health and longevity. If you have to ask for internet advice, maybe you aren't ready for undertaking this task and an arborist should be called. Late winter is tree-pruning time for most trees. Spend an entire evening looking at YouTube videos on the subject. If you still aren't sure what and when to prune, please call an arborist. It is money well-spent since it prevents more costly problems later.

This link will help you.
https://www.gardeningknowhow.com/ornamental/trees/oak/live-oak-tree-care.htm