If that doesn't help, try a totally fresh install of the game after backing up your saves:

• Backup your save game(s)
  
• Uninstall Valheim through Steam
  
• Manually delete the game's install folder (C:\Program Files (x86)\Steam\steamapps\common\Valheim)
  
• Manually delete the save folder (WinKey-R, type in 'appdata' without quotes, double-click LocalLow, find "Irongate" folder and delete it )
  
• Clear Steam's download cache using these instructions[heroesandgenerals.com]
  
• Reinstall the game fresh
  
• Validate the files through your library / game properties
  
• Try running it with standard settings (don't modify any) and see if you can create/start a new SP game without crashing.