Update : Definitely something to do with the network.
Here is what the texts I have done and the outputs .
1. Created a another VM with swap file in the same location as with VM - initiated a Vmotion
Ran esxtop : we see packet drops of 100% and the VM still rebooted.
2. removed the vmdk from the test VM and migrated it - did not reboot the VM.
removed an existing VMDK from a production test vm and migrated and it did not reboot. Seems the VM gets rebooted after the stun of the VM at the end of the migration.
We are checking the network to see what is causing the problem and why is the saturation occurring.
Thanks,