Step 1: Immediate Workaround & Confirmation
Use a USB-to-Ethernet or USB-to-WiFi Adapter. If the problem disappears entirely with a dongle, you’ve isolated the fault to the motherboard’s internal LAN hardware or its power delivery. This is a strong data point.
Step 2: Investigate Power Supply (The Most Likely Culprit)
Visual/Smell Check: Power off, unplug, open the case. Look for any bulging or leaking capacitors on the PSU (don’t open the PSU itself) and on the motherboard near the CPU (VRM) and PCIe slots.
Listen: Under load, do you hear any faint high-pitched whining or buzzing from the PSU or motherboard area? That’s coil whine, often associated with power issues.
The Definitive Test: Swap the PSU with a known-good, adequate-wattage unit. This is the most reliable way to test. Borrow one if possible. If the problems vanish, you’ve found the culprit.
