There’s a post here https://forum.obsidian.md/t/obsidian-screen-goes-black-seconds-after-opening/71926/2 where a member pinned it down to a bunk .md file.
I managed to do something similar once with a 2MB .md file full callouts and embeds repeating over and over. That vault was just a gray box when opening; no window buttons as all. Other vaults opened normally. Other apps froze as well when trying to open it - only BBEdit was able to open the file with without issues.
So one thing to try is, using the system file explorer (outside of Obsidian), look for any files that seem unusually large and move them out of the vault. It’s worth a shot.