This morning I was working on my site and it suddenly started dropping 500 Internal Server Errors left and right. Anyways, here's some things I did that helped:
Increased the memory limit. As default it was about 90 MB and I bumped it up to 256 which is much more than I need.
Repaired all the database tables and optimized them too. Also I noticed there was a table leftover from a deleted plugin (I tried it and it wasn't really that good) so I deleted that (I did a backup first though).
I use all my plugins. So here's what I did:
-- I had a couple of redundant ones (e.g. I dont know why I had 2 contact form plugins.). I searched the plugins to find one that would do the features of both and reduce the amount of plugins. Actually for the contact form one I just switched all the other forms to one system.
-- Some of the plugins I used, but not all the time and it wouldn't break functions or shortcode or something if I deactivated them. So I deactivate them and turn them back when I need to use them. For example, a maintenance mode one and a search and replace one.
Remove .htaccess and then redo the permlinks. This didn't really help me much but I read a misconfigured htaccess can make that issue.
Also check cache plugins. I deactive it and a lot of the errors went away. I'm currently tinkering with other ones now to see which works.
Then I waited for a few minutes and it stopped doing the errors. I hope this help someone else.
If anyone wants to post more ideas do that here.