Possibilities to consider:

• Vents and heatsink fins clogged with dust; needs a careful clean-out.
• Dry thermal paste or warped heat pipe reducing heat transfer.
• Fan failing or fan curve stuck; BIOS/EC or replacement might be needed.
• Background load (malware, runaway updater) keeping CPU/GPU pinned.
• Using on soft surfaces blocking intake.

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What it might be (likely causes)

• Airflow blockage
  Lint cakes inside the fan shroud and radiator fins, choking airflow. Even a thin felt layer can push temps to throttle or shutdown.