When Morrowind was first added to your account, there should have been a single mail with 'An Invitation to Morrowind' letter (at least that was my experience). Reading that letter sends you to speak with an NPC in Seyda Neen. The letter can be banked, so it may be possible to share it among your characters.

As far as an NPC to send you there like they did with Thieves Guild, Dark Brotherhood and Orsinium, no there is not. You'll have to use the aforementioned letter (which may also be posted near the boat(s) which travel to Morrowind) or see if there is a starter quest option in the store.

FYI, the prequel quest is not required to start Morrowind but may make sense to do it before hand.