Hi Swadha Srinivasan,
Thank you for reaching out to us on the Microsoft Q&A forum.
The VM stopping is a planned activity and it is done by the authorized user.
You can find it by the navigating to the activity log here you can see the who stopped the VM.
Also, you can check it in from the left side blade click on resource health here you can see the complete root cause analysis (RCA) of the VM.
Please find the below screenshots for your reference:
If the information is helpful, please consider by clicking the " Accept answer and Upvote " on the post.
If you have any further queries, please let us know in the comment.