I'm going to take a chance at a possible cause since diagnosing the problem is very difficult based on your description, as you mentioned.
I suspect it is an automatic resetting circuit breaker or transformer, since the power comes back on without any action on your part. I mention transformer since it may be with the local power company, or within the park's electrical system. You mention sometimes it would only include one half of the trailer. Since your trailer probably has 50 amp service, which is actually two 120 volt feeds, one of the feeds may have been interrupted while the other feed was not. That would indicate a problem with the power coming into your trailer, not in the trailer itself. Most RVs with 50 amp service have both circuits connected so that both trip off together.