@DharaniRaaj next time you encounter this scenario, can you please attempt to capture a memory dump of your web app before restarting the app? We have built in memory dump collection and analysis into Azure Web Apps. To do so, please follow the steps listed at this blog.
Please let us know the outcome as it sounds like something within your code is hanging due to a possible deadlock or another issue.
Also, before generating the memory dump and restarting the app, I would suggest looking at cpu and memory consumption. Are these metrics high?