Hi Nilesh Dhimar,
If your Virtual Machine getting stopped/deallocated there might be few reasons, please check below:
Azure has Auto-shutdown feature, see if it is enabled in your system and disable it. Go to Azure Portal → Navigate to your VM then under Operations, click Auto-shutdown. If it's enabled, turn it off.
To disable Auto shutdown, please check this previous similar issue: Azure virtual machine stopped / deallocated
For detailed information about Auto shutdown, please refer to this Auto-shutdown a virtual machine
If you are using a Spot VM, it can get deallocated when there is a capacity shortage in the selected region. Try resizing the VM to a different size or try to move the VM to a different region. You can also create a new VM as a 'Standard' virtual machine and can snapshot your existing disks and create a new VM from these.
For your reference: Use Azure Spot Virtual Machines, VM stops randomly
If your subscription credit expires or billing fails, Azure may stop (deallocate) your VMs. Go to Azure Portal → Cost Management + Billing → Ensure your subscription is active.
For your reference: Azure subscription and service limits, quotas, and constraints
Once check Resource limit or Quota if you have exceeded. Go to the Azure Portal then navigate to Subscriptions > Usage + quotas. Check if you've exceeded any limits. If you're near or over the limit, request a quota increase from Azure Support.
Detailed information to Increase quota: Increase regional vCPU quotas
Go to Azure Service Health to see if there are any maintenance events affecting your VM. And also, check Activity Log under Monitoring tab to see the logs.
If you have any further queries, please let me know. If this is helpful for you, click on Upvote to let us know.