The problem that's causing a slow start might be related to file corruption or an antivirus solution that's blocking major processes of the Bluestacks application. The first thing I would try is to reinstall it. Completely, remove the application after you have backed up the files to a cloud service or something related.
After this process, remove Bluestacks then download a new version. Additionally, use the antivirus solution and add all the Bluestacks executable files to the Exclusion list. You can find them in the Bluestacks installation directory.
