Dell SA keeps telling me "no bootable devices found" and shutting down

Periodically Dell Support Assist / Onboard Diagnostics kicks in, scans my computer, and tells me "no bootable devices found" and then shuts down. When hit the power button it starts right back up and reboots like normal.

I had gone to BIOS and checked the Boot area and do not recognize what the boot preference -- no option to select harddrive or C: 

I had earlier uninstalled Dell Support Assist to get rid of periodic blue screen with different error message but it appears that SA is still out there. 

We have purchased a number of Dell computers and never had this issue -- please advise me if there is a fix for this.

Thanks, 

JTPerry