Here is a list of things you need to do:
- deactivate all plugins
- download WP Super Cache (or anything like that)
- if you have the Jetpack plugin, delete it. It causes lots of problems.
If that didn’t work, are you having some errors sometimes that show up on the top of the screen? If so, tell me, and exactly what is written there.
I had this problem a long time ago and then I put a piece of code on a file and then it went faster. But now I forgot the code.
I will try my best to help.