I have seen several problems cause logins to exceed reasonable time frames:
1) The server running the Server Tools portion of SAP is having a problem, therefore validating the users License causes a slow login.
2) New alerts were added and set to fire off early in the morning. SAP, during and right after login will try to execute all those queries slowing down the login process.
3) You may be experiencing a problem with an add-on. What add-on’s are auto starting, and through process of elimination, temporary disable those add-ons to see if login time improves.
4) Is this login issue for all users, or just a few? If it’s just a few, those particular users may need to have their %temp% space in relationship to SAP cleaned up. Re-installing the client can help to resolve that as well.
Hopefully this gives you some ideas as to where to look.