In a

beforeSubmit

or

afterSubmit

user event you have access to

context.oldRecord

and

context.newRecord

. Get a list of items with the column fields you are interested in from each of newRecord and oldRecord. Compare the lists, and if there are any differences according to your requirements use

N/workflow#initiate

to start the workflow (or

N/task#create

to start it asynchronously, if it could take some time to complete)