

What’s your utilization? On how many cores?
Starting blind, I’d start with cleaning the case, fans and heat sinks with compressed air (canned is fine, do it outside). Dust builds up, and prevents proper cooling. DO NOT LET THE FANS SPIN WHILE CLEANING THEM, the reverse current will damage your system.
Check for any failed fans.
After that, changing the thermal paste might help depending on how well or how long ago it was applied originally. Paste is cheap so no need to be stingy. Generally lasts about 5 years before beginning to degrade.
That there is. It’s going to be an… interesting 4 years. And an even more interesting time clean up the mess afterwards.