It could signify a hardware failure or corrupted files.
Could you identify the pattern of the start-up beeps - this article explains what they may mean.
Did start-up repair show at all to look for startup problems?
You say that there is a backup already on a USB stick. Is this USB stick used only on this PC? Has it ever been put into another PC?
If the PC is operating ok for the moment you could try running the free Malwarebytes - here.
You could first of all try a Start-up repair.
You will need your windows 7 disk or the recovery disk that you may have made. This article will take you through it step by step.