Time Machine Backup Eject Notices

I keep getting multiple Time Machine Backup eject notices every time I bring up my computer from sleep! I click on one and they all go away.... I have not ejected the backup disk. Could it have been from a power failure? How do I stop them from coming up?

If you have not done any troubleshooting (it seems you have not) please start with a SMC reset, it may take 2-3 attempts for the reset to work.