Ceiling light goes off itself
Heat is an enemy for LED bulbs, and many bulbs say specifically that they cannot be used in an enclosed fixture since there is no airflow and a build up of heat.  I tested this with some LED bulbs from IKEA, and sure enough, in an enclosed fixture they would turn on and off as they heated up.

It could be that your bulbs used to be fine, but the heat has slowly degraded them.  Check the bulbs and see if they mentioned use in an enclosed fixture.  Either way, replacing the bulbs with the appropriate type is probably your best bet.