My keyboard and track pad do not work my MacBook Pro

After turning on my MacBook Pro 2015, a pupup says my MacBook can’t find Bluetooth keyboard. I don’t use a blue tooth keyboard. If I connect a usb keyboard and a Bluetooth mouse I can work the machine. Sometimes the computer works fine, but most of the time the pop up comes up. The pop up also comes up without restarating the compuser. Is there an easy fix for this problem?