MSI 1761 keeps rebooting. Failing GPU?

[Infernal12]

Hello everyone, my MSI 1761 with i7 2630qm and GTX 570m has started rebooting randomly the last 5 days.
I have made some tests to single out a few things that could cause the problem
1) Changed OS
2) Memtest
3) Different power supply
4) Battery only

I could be just browsing the net, not even stressing the GPU and just shuts down and reboots with no error whatsoever. Sometimes when it reboots and cant even get past the BIOS and it may restart 4-5 times before I even see the OS selection screen.

The rig is practically unusable untill 10-11 in the night which points to a temperature problem I guess.
The GPU idles at 42c and the CPU at 43c.

Am leaning a lot more towards the gpu because it already failed once 2 years ago and I replaced it with a used one from ebay.

I also run Valley benchmark and strangely enough it run for about 5 minutes at 80c before it rebooted.

Any ideas?

Do I have any other options other than dishing out another 300 and wait 2 months for another GPU on a 6 year laptop? Are there any other cheaper compatible graphics cards?

I really dont know what to do, I dont want to waste money either on an old laptop nor on a new not really wanted system.
The blood thing doesnt even have onboard graphics so I can do basic stuff.

Thanks in advance.

Edit: To be honest I dont know what the problem is anymore. Could it be the CPU?
I ve gone a whole day without any reboots but other days it reboots even when both the cpu and gpu are and 40c and 5% usage. Could it be any of my 2 ssd's. Maybe something drawing too much power on the motherboard?

[Polip]

Possible problem with not enought energy from PSU or battery during high needs of performance

Edited October 20, 2017 by Polip