This was the case with the community edition. Can't exactly pinpoint the reason out. Even if the cluster gets terminated because of inactivity, you still have to create a new cluster again from start. Will post the exact reason why this is happening in some time after some research. FYI..this was the case with me and most others too.. :).

https://stackoverflow.com/questions/69072694/databricks-community-edition-cluster-wont-start