I have a cat that has been neutered and on occasion he will bite me for no apparent reason. I’m not petting him or anything. This almost always happens at night. Why is he doing this and how should I respond?
Cats bite for a number of reasons. The most common are probably fear or over stimulation, but that doesn't seem to be your cat(neither normally causes a cat to seek you out to bite). Age can also be a factor, with young cats sometimes biting as a form of aggressive play (if that sounds like your cat, then you'll want to look for information on a common issue called, "play aggression"), and older ones sometimes biting due to confusion caused by neurological or sensory issues(If this may be the case a visit to the vet is in order.)
There are three other relatively common issues that can cause biting. Declawing is a common cause, especially in cases where complications from it may be causing chronic pain. If your cat was declawed, you may want to take him to a vet who does restorative surgery on declawed cats for evaluation. The Other two are redirected aggression ( my guess in your case), and status aggression.
Redirected aggression is a very tricky form of feline aggression where the cat is upset by something (often an outside animal) and then acts at at whoever is closest (frequently their human caretaker.) I suspect that may be the cause, because you say it happens more at night, when several animals are more active (racoons and other cats, for example.) Try and see what sounds you can hear when your cat attacks, and if it is other cats or racoons, you might try making your yard less hospitable to them by securing garbage cans, adding motion sensor lights, etc.
The last possibility is status aggression, which means that the cat may believe that they are dominant over you. The solution that is frequently suggested is training the cat to do tricks in exchange for a small treat. If done regularly will help to reinforce the idea that you are in charge without making your cat afraid of you ( which almost always increases feline aggression.) Clicker training is especially recommended for status aggression, but you can use more traditional methods and still get good results with effort, if you prefer. Whatever you do, don't respond to their aggression with your own, as that tends to exacerbate matters; just do the training, and, if necessary give your cat a short time out in a safe room for a few minutes to calm them if they are too aggressive.
If you aren't sure as to the cause, reducing outside sources of stress for redirected aggression can obviously be done at the same time as treating status aggression with some clicker training. Both will help make most any cat calmer and less aggressive, and neither should cause problems.