When opening Minecraft and clicking launch on Minecraft 1.13.2 (including snapshots) my computer freezes up and goes at around 3-5fps. I tested on various other computers and it's the same story. Once the game loading screen (Mojang screen) appears the lag stops and returns to normal. I've talked with other friends and thyey have the issue.

I've tested with Optifine aswell and the lag isn't as intense with that mod.