Draugr sometimes say “Unstaad Krosis” when attacking. I understand that means “many apologies” in dragon tongue (convo with Paarthurnax).
Does this hint that they are doing something against their wishes?
[Not a complete answer, but too big to be a comment.]
However, the draugr were in life the servants of dragon priests, and upon their priest’s death they would be entombed with him as his eternal servants and guardians; there appears to be nothing unwilling about it, and the lore article even specifically debunks the common Nord misconception that draugr are cursed. Draugr are, in fact, the undead servants and guardians of their immortal dragon priests.
This leads me to conclude that they are not, in fact, apologizing to the Dovahkiin as they attempt to disembowel him/her, especially alongside another common phrase listed in the aforementioned lore article, Daanik Ah Dov, or “Doomed dragonhunter”, which appears to clearly be a threat.
I cannot, however, offer a clarification of the meaning of Unslaad Krosis in the context of the draugr mutterings, other than to offer my personal observation that dragon language appears to be at least somewhat idiomatic, and that oftentimes words seem to have deeper philosophical meanings than what a direct English translation would suggest.