Quick save closing game
Solution 1:
There are two ways in which you can stop this:
Go into settings and disable all kinds of autosaving. That means Autosave on travel, Autosave on rest and autosave in the menu. Leave your current location so that you can fast travel anywhere, select one of the major cities like whiterun, solitude etc Cross your fingers and try to quicksave. This answer was found here
The next way in which this can be fixed is: Delete your quicksave file and then quicksave again. Make a backup first just in case. Apparently the save files have issues if they're overwritten too many times. This answer was found here