Did you by chance change your data strategy to start using live connections to your database? Or did you start running a ton of extracts? Or did you publish a workbook with 20 live connections being leveraged by 4 simultaneous users?
tabprotosrv is the process that is the intermediary "middleware" between your server and your database. So each tabrotosrv can represent an active task or can indicate a previous active task. So if your workbooks have multiple live connections and are being rendered by multiple users, then there will be a lot of tabprotosrv processes, or if you have lots of extract refreshes, then tabprotosrv will be leveraged to get the data and refresh the extract.