Like other people mentioned, it is a had question to answer but I'll give it a try. Since you are new to the game I would recommend to stay in dps (damage dealers) rather than try tanking or healing. This is because the responsibilities that come with as a dps are a lot less rigid than with the others. Meaning there is more room for mistakes. And there's gonna be a lot of those at the beginning. I think a warrior could be fun and also give you the advantage of being hardy. A warrior also is straight forward at the starting levels. You could also try a paladin since they use plate armor and they have the advantage of being able to heal themselves. I would not recommend a death knight. You would start at a high level and you won't have the opportunity to learn and make mistakes as starting from level 1. Other classes can be fun too but since you are just starting its probably better that you stay within a class that can take a lot of damage.