Dust-clogged fans and degraded thermal paste can also be a factor, particularly after 3 years. iFixit guide for removing your heatsink: https://www.ifixit.com/

Dust-clogged fans and degraded thermal paste can also be a factor, particularly after 3 years. iFixit guide for removing your heatsink: https://www.ifixit.com/Guide/MacBook+Pro+13-Inch+Retina+Display+Early+2015+Heat+Sink+Replacement/45130 https://www.ifixit.com/Guide/MacBook+Pro+13-Inch+Retina+Disp... My favorite thermal paste: https://noctua.at/en/nt-h1.html https://noctua.at/en/nt-h1.html