Hi. My name is*****'m a camera repair technician with over 20years in the business and I'll be glad to help you with your question today.
This is the infamous AF motor malfunction Nikon lenses are famous for. The only cure is to replace the AF motor. This really isn’t a user serviceable problem as it requires disassembling the lens and should be repaired by a qualified technician. You may want to check locally for a camera repair shop in your area, or, if you need assistance finding a shop, please let me know and I'll locate one for you.
With most shops, it will depend on whether it is the VR lens or not. If you look around a little, you should be able to find one to repair it for around $65.
Just a note to see if I can be of any further assistance?