There are far too many possibilities to really give you anything that will certainly solve your problem. One relatively common bug can be fixed simply by letting your game load, then letting your character die and the loading again.
The most common reason for this (for the record) is a corrupted save file, which has been a problem with games on this engine since Oblivion and it is only made worse by mods, especially if you commonly add or remove mods during the course of a game. If you play with mods, it is best to determine what configuration you want to use at the start and then not alter them unless you start a new game. There is no known solution to a corrupted save nor is there an easy way to identify if your save is corrupted. The only thing I can tell you is to load the last save where the game worked properly and play from there.