If you say the issue is intermittent and when the site does not work it redirects you to wp-admin/install.php it is very likely that you are hitting the maximum number of database connections set by your hosting provider. Once you hit the limit the site won’t be able to connect to the database and will redirect you to the install page, after one hour when the count resets the site will work again until the limit is reached and so on.
You might be reaching the maximum number of database connections for many reasons, but these are the most likely:
- Your site gets a lot of traffic, or at least picks with lots of traffic
- You are experiencing a small ddos attack
- Your themes or one of your plugins has a bug that is causing an excessive number of database connections.
If you don´t think traffic is the issue then try deactivating your plugins see if that fixes it, if it does then activate them one by one until you find the one causing the issue and replace for an alternative one.
If you find that plugins are not the issue either then definitely contact your hosting provider explaining the situation.
Good luck!