I had a contrator put in a BBQ area and pergola for me. A couple of weeks
ago the lights stopped working. The contractor sent the electrician who did
the original electrical installation to fix it. He pressed the GFCI button
and the lights work again. I asked him what the cause of the GFCI resetting
and he said "they do that". I think it was just a symptom of another
problem, possibly related to the heavy rain that we have had recently (as is
usual in Texas).

Is GFCI designed to spontaneously reset? If not, what is the cause of this?

Thanks!