They delay between steps 5 and 6 is most often related to number and consistency of Provisioning Roles or when importing large number of endpoint definitions into your IME.
This delay is not uncommon as IM r12.6 object cache is built between steps 5 and 6. (as well as used for setting the tenant key) - and the delay experienced is often found in building the screen cache.
Executing the following SQL on the object store database should dramatically decrease your startup time.
-- Adding indices for Objectstore tables IM_SCREEN_LD & IM_SCREEN_FIELD_LD
create index [idx_IM_SCREEN_LD] on [dbo].[IM_SCREEN_LD] ([REF_ID])
create index [idx_IM_SCREEN_FIELD_LD] on [dbo].[IM_SCREEN_FIELD_LD]
Before any changes are made to Production database, please ensure a backup exists in place.