Good day @NikaraWorld
auto restarts... Reboot...
Azure Spot VM do not restart but shutdown when Azure needs the capacity back. This means that it will Deallocate (moves your VM to the stopped-deallocated state) or Delete the VM according to your configuration.
Moreover, before it evict Spot VMs you have a 30 seconds notice, and you can opt-in to receive in-VM notifications through Azure Scheduled Events, as explain here.
Therefore, according to your description this issue is not related to the Spot (assuming the description was accurate).
Reboot initiated from inside the machine(Customer Initiated)
This fits the explanation I gave above.
You should monitor the internal of the VM and other options that might send a command to schedule the machine