Dead mobo's after shutdowns

So this problem has happened to me twice and so far I haven't been able to determine what exactly causes this to happen.My computer will be left on and running perfectly will no issues whatsoever.However, after turning it off for the night I wake up and it won't post/boot anymore when turning it on(still receives power however).I believe something is killing the mobo, since after the first time it had been working again after that.But with it happening I guess I just wanted to know if anyone had an idea about it?

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Power-up issues like you're describing, at least in my experience, are almost always the result of a cheap/bad mobo, loose connections to the mobo (bad RAM, e.g., or half-seated expansion cards), or a dying power supply.