The storyes are not conected.
But i strongly advise playing Morrowind because it's such a good game...Better that Oblivion IMO.The graphics can be a litte out-dated,but there are some really good texture packs that can make the game feeling much better.Ultimate Texture packs are really good for example.
Morrowind has more quests,guilds,fantasy,its superior in so many ways.
Absence of voice-acting can be a problem though.Sometimes you can get the feeling you are in a ''dead'' world where nothing happens,if you don't trigger it.The game can be frustrating sometimes,but the next time you turn on the game it becomes intresting.I got that feeling from probably playing too much.
Oh yeah.and get the expansions.I'm sure you won't be disapointed.....Both Trubunal and Bloodmoon are even more intresting than the original game (IMO).
Mournhold! City of Light! City of Magic!
And you will be absolutly charmed with Solstheim (Bloodmoon).Nord villages are charming,East Empire Company quests,and offcourse the Bloodmoon Main Quest.You can become a werewolf i it.
So i say go for it!
Playing Morrowind never hurt anybody!