Question PC crashes often and restarts right after.

Mar 15, 2020
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Its not an old pc its half year old (only the hdd and ssd are 3 years olds cause i took them out from my previous pc). so the problem is that the pc crashes it makes a noise for 2-4 sec then restarts in like 5 seconds and its full random when it does that. it started a month ago and i tried a lot of thing: downloading everything that was installed around the time it started, i cheked maybe its a virus with 3 different antivirus but nothing, i deleted the windows 10 updates, i reintalled the full pc so now i only have the full minimum. But it still crashes.
Ideas whats wrong?