This is a pretty normal feature of Morrowind, even on today's high end computers apparently.
If you are on PC, there are things you can do to make the game run more smoothly.
First of all, turn off any and all malaware scanners... For that matter turn off whatever does not absolutely need to be running.
After that, you can also tweak the game,
this site has a lot of useful information on how to do that.
Finally, I would also recommend a RAM optimiser of some kind. I use
RAM idle Pro and
Fast Defrag.
I have a Pentium 3 and 384 MB of RAM, along with a relatively low level graphics card..(NVIDIA GForce FX 5200) but with taking the above measures I can run Morrowind fully loaded with over 100 mods tolerably well. It's not lightening fast, and load times can take a while, but all things considered, it's surprisingly good.
By the way, which version do you have?
Just Morrowind?
Both expansions?
Just one expansion?
Make sure you grab the right patch... If you have the Game of the Year Edition (original game and both expansions), the installation order is as follows:
1) Morrowind
2) Tribunal
3) Bloodmoon
4) Bloodmoon Patch
In the above setup, do
not install either the Morrowind or Tribunal patches, you don't need them and they could screw up your game. You only require the Bloodmoon patch.