Hello, problem is, that I need to render old project and when it stars to render my pc restarts. Couple month ago same project was working fine.
There is nothing in Corona that can cause a restart, or a “blue screen of death”
So, unexplained restarts are usually either Windows doing one of it’s automatic updates but this should just be a one-time thing and not a repeating issue. If it repeats whenever your machine is running for a long time under high load (e.g. when rendering) then I’d say most likely a hardware issue e.g. overheating, a RAM or a hard disk error (causing a crash when some part of RAM or some place on disk is accessed), or maybe even a driver issue perhaps.
Could be worth looking into programs that stress test the machine so you can watch for errors and see which is the cause. I hope you find the cause and a fix for it!
If it is happening as soon as the render starts, and only in this scene, then shouldn’t be high load - could be plugins, or something else causing the host application to fail? Any error message that goes with it, or a crash dump from the software?
I gave my computer to warranty and they say everything is fine. Pc is brand new, have great spec. i7 8700k, 32ram.
When i render with vray everything is great, but when i start corona render, my pc restarts 
Again, Corona can’t cause restarts, so has to be something else - more information needed though. Is this every scene, or one particular scene? The title of the thread says “when you leave it on for rendering”, but the post says “as soon as you start rendering”, so would need to know which it is. Is there an error message before the restart? Cheers!
In every scene. when i leave for rendering, somethimes pc restart after 5min. rendering, somethimes after 1hour.
Definitely sounds like a hardware issue I am sorry to say. I would look into setting up things like temperature monitoring, or running stress tests on the machine. New or warrantied or not, hardware can have faults unfortunately Sorry you are having the problem. The developers can give the technical ins-and-outs of it all, but from my non-developer understanding, Corona isn’t tied into the OS in a way that can cause a blue screen of death or a restart - it can however stress components and if they overheat or have some error, that can show up when rendering while everything else seems normal under regular use.
Bad news..
But thanks for help!
NP, and yes, sorry the news is bad - could be just a driver thing though, so maybe not as bad as needing to replace hardware components. I think stress testing should help find out the possible cause - keep us updated on how it goes!
look at system logs, it can give a clue
Some times ago i have same problem/
may be you have to check a processor overheating, in long time render with 100% usage:)
If Error Report shows up, post it here & send/show it to your PC servicer…
Overheating would be my first bet.
Please monitor your CPU temperature with some free soft, e.g. Core Temp. I think it even has some basic logging feature, so it can store your temperatures in a file so that you can inspect them after the restart.
Another idea would be to replace the radiator or thermal grease.
while rendering i always check my cpu heat in SpeedFan program, and my cpu never goes more than 51C
Do you have all drivers and BIOS up to date?
i think so 
i only update intel drivers, for now i dont have grafic card
i think so
i update my intel driver, for now i dont have grafic card
maby problem in windows
The CPU and system is overclocked or no?
no
i believe it gives you death screen and reboots. just read system logs what cause, it may be ram issue or other hardware fail what need to check