How long has it been since you played? There was an update a couple weeks ago that broke all the mods, because it broke BepInEx.

I'm not even modded, and I had some crashing issues after that update. What worked for me was to uninstall Valheim, then delete the Valheim folder from "C:\Program Files (x86)\Steam\steamapps\common\", then reinstall.

The save files are located elsewhere, so my characters and worlds were fine afterwards.