Do vampires in the Elder Scrolls universe need to sleep? The closest information I could find was this dialog from the game Skyrim, spoken by Lord Harkon:
With the world in shadow, we would never tire, never weaken... more than a match for their pitiful armies.
The context is Lord Harkon speaking about the effects of blocking out the sun by firing Bloodcursed Arrows at it with Auriel's Bow. That statement makes it sound like vampires don't need to sleep—they simply need to avoid sunlight to keep from tiring. But perhaps the magic of using Bloodcursed Arrows with Auriel's Bow has an invigorating effect on vampires directly, in addition to blocking the sun. The prophecy related to blocking out the sun is vague enough that it's hard to tell the exact results predicted.
In the game, Castle Volkihar has coffins, so the Volkihar vampires at least have somewhere they can sleep if they want to. I don't know whether Skyrim programs any vampire NPCs to sleep during part of the day, but the game is inconsistent about sleep cycles: even some mortals are never seen to sleep, when realistically they would have to eventually.
Do vampires have any need to sleep when the sun isn't blocked out by using Auriel's Bow? Does it depend on the tribe of vampire or strain of vampirism?