MongoDB: enable sharding automatically
No it is not possible to automatically shard the collection. This is what you have to do per collection.

Ref:


https://docs.mongodb.com/manual/reference/command/shardCollection/
https://docs.mongodb.com/manual/sharding/
https://docs.mongodb.com/manual/reference/command/shardCollection/#dbcmd.shardCollection


You will need to run shardCollection command in order to shard a new collection.  The collection must have an index whose prefix is the shard key.
The following operation enables sharding for the people collection in the records database and uses the zipcode field as the shard key:

use admin
db.runCommand( { shardCollection: "records.people", key: { zipcode: 1 } } )



  Shards a collection to distribute its documents across shards. You
  must run enableSharding on a database before running the
  shardCollection command. The shardCollection command must be run
  against the admin database.


A database can have a mixture of sharded and unsharded collections. Sharded collections are partitioned and distributed across the shards in the cluster. Unsharded collections are stored on a primary shard. Each database has its own primary shard.