Why computer says usb over detected shirt off 15 sec

This is the day for funny typos, flush drive, shirt off.

Unplug whatever you have in the USB ports and reboot. If that does not fix it, your USB ports are probably fried. You may be able to get around this by disabling USB in the BIOS, if not you need to bring the PC to a technician to replace the motherboard. The message comes up if the computer detects too much power going to the USB ports, that tends to do some heavy damage to them.