Quote (Secksii @ Feb 21 2019 09:41pm)

it's the screw that goes between your motherboard and the case, to prevent a short when you turn on your computer.

i'd also take out all your ram, and try using 1 stick at a time to eliminate a faulty memory slot or memory stick itself can be bad.

just diagnose it one thing at a time, i highly doubt it's a power issue though. You have a very high quality 550w psu and you're not overclocking anything so it's more than enough.
disregard what the gpu box says about 1080ti needing 600w or whatever, they purposely over-estimate the power required to run it cos they have 0 fucking clue what other components you have.