This has been happening since the last update. Also related to https://vrchat.canny.io/bug-reports/p/with-full-body-tracking-when-loading-into-the-game-for-the-first-time-or-switchi but the problem with that one is actually calibrating before it allows you to move, so when your avatar loads it's already calibrated all screwed up. The real issue for that is this, that you can not move at all when you first load in or sometimes even when switching avatars.