Have you tried reseating the RAM and the graphics card?
Remove all RAM modules and the graphics card, use a can of compressed air to clean out the slots and the contacts, and then replace the RAM and the graphics card.
As you add and remove hardware, follow these steps for ESD safety:
- Shut down and turn off your computer.
- Unplug all power supplies to the computer (AC Power then battery for laptops, AC power for desktops)
- Hold down the power button for 30 seconds to close the circuit and ensure all power drains from components.
- Make sure you are grounded by using proper grounding techniques, i.e. work on an anti-static workbench, anti-static desk, or an anti-static pad. Hold something metallic while touching it to the anti-static surface, or use an anti-static wristband to attach to the anti-static material while working. If you do not have an anti-static workbench, desk, or pad, you can use your computer tower/case by finding a metal hold in it, such as a drive bay.
Once these steps have been followed, it is safe to remove and replace components within your computer.