While playing vanilla Minecraft 1.21.3 or 1.21.1 in single player, every 15-20 seconds or so theres a lag spike where the GPU goes from 25% with 50 fps to GPU at 1% with around 20 FPS for a second. The ram was increased to 7 gb and it helped a little but the problem still occurs regularly. Lag spikes occur more when loading chunks but still happen when not moving at all.

Impacts 1.21.3 and 1.21.1

Does not impact 1.16.5 and 1.20