It could also be due to other devices on your network having a static IP address and this being the same as yours. So it drops yours when they get turned on. A good culprit for this is a printer.
But let us know the ipconfig /all results when it occurs and it will much easier to troubleshoot. We'll stay tuned.... I realise that this can take a while
EDIT: hmmm there should be a pop up warning for this scenario though.