You may be partially right with the relay.... it sounds like either the relay is sticking, or you have an intermittant blower motor (the windings may be starting to open) or some bad wiring somewhere. Now, the fan speed switch on the dash.... does this happen in all 4 speeds or just on one or two of them. I do know that the resistor grid on older Honda fan speed controllers tend to go bad. They can either blow a resistor or a contact can become intermittant/corroded (moisture, temp. extremes, etc.) If I were you, I'd buy a Chiltons manual (or similar) and check all the things I mentioned to you about.