Check for Foglight repository database performance issues (FMS logs, Datasource auto thread dumps). May also want to check for any deadlocks.
The Foglight account used to login may have a homepage that is slow.
Resolve the database performance issues via configuration settings or reduce I/O.
Use another account with a different homepage. Preferably a Foglight core out of the box dashboard (administration dashboard for example or default welcome page).
Engage Foglight support to check for any current Foglight performance issues and/or review the Foglight Management Server support bundle.