I have a GFCI outlet out by my pool. I have a timer switch inside that sends power to that outlet. My pool pump has a plug that is GFCI (I assume that is what a plug is called it has a test and reset button). Whenever my timer switch sends power to the GFCU outlet my pool plug GFCI trips. Push the reset and everything is fine. Unplug it and plug it back in works fine no problems. The only time it trips is when it is plugged in and the GFCI outlet receives power.
What is causing this and how can I fix it?