There is a lot of balloon activity on this VM, Which means that the ESX server is running out of memory. You must have overcommited the Memory.
solution:
1) You could consider moving this VM to another ESX server which has better memory resources.
2) You could increase the memory reservations for this VM and ensure that this VM gets a specific amount of memory all the time wether it uses or not. This might cause performance issues with the other running VMs on this host.
3) If this VM is in a DRS cluster. DRS should have taken care of moving the VM across all the possible servers as and when you are running out of resources. If you Virtualization environment is already DRS enables and you are see this issue which means your are running out of resources. The solution would be either increase RAM of few machines in your environment or introduce a new server in the DRS cluster.
Let me know if this helps.
-Surya