I dont know whether it has something to do with the qlikview services not responding but other than this I didnt observe any unusual event. This is happening frequently. Can someone please help regarding what should be the reason behind services was not responding and restarting them worked.
Have you check you log files to see if you can see anything there that will give you a hint?
It is surely a RAM based issue and increasing Virtual Memory is also not a Permanent Solution.
Since Qlikview is a RAM based Tool, I will suggest you to increase the RAM and Memory size.
It will definitely fix your issue.
Make sure the QVS logs are set to high in the QMC. This will cause a restart so need to make sure you do this after hours. Then the next time it happens check the logs.