1. Please clear CMOS.
2. Please take out your memory cards and video card, try to clean their golden connectors with a rubber, then reseat them back.
3. Please take the CPU cooler out, add some thermal paste to the CPU surface, then reseat the cooler back and keep the cooler tightly installed.
4. Please keep the necessary components(CPU, one memory) onboard for a test.
Finally, we would recommend you to replace a BIOS battery to have a test.