When you open a solution you are working with normally Visual Studio will open all the opened files you were opened in it. But if that is not happening there are two reasons why that did not happen.
1. .suo file may be corrupt
Just delete the .suo file and Server folder inside SolutionFolder\.vs\FolderWithSolutionName\v15\ open the visual studio open files and see visual studio remember them
2. Disabled in options
Tools => Options => Project and Solutions and make sure that “Reopen documents on solution load” is checked
Second one was my issue.
If you do not want Visual Studio to remember the opened files you can set the “Reopen documents on solution load” option unchecked.