What is the Make and Model # of your Intel Arc Motherboard?
A computer that shuts down on it's own is overheating or there is an issue with the PSU. Open the case and clean out all dust and blow out all fans with a can of compressed air. If it continues, download Hardware Monitor and check the temperatures when using it or gaming Open Hardware Monitor - Core temp, fan speed and voltages in a free software gadget. If it is overheating You may need to reapply Thermal Paste between the Heat Sync and the Processor. If that still fails and a tech has determined that it is the Motherboard that needs replaced, then I would believe them. You can always take it to another computer repairman for s second opinion.
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