It sounds like the auto reset circuit breaker on the battery terminals is tripping out due to too much current being drawn which trip out circuit breaker. A few seconds later the circuit breaker will cool down and auto reset allowing you to try it again...
Something may be dragging on the slide out. Maybe some lub is in order. It could also be a failing auto-reset circuit breaker.
Another fix I have done here was to provide more current by nosing my truck up close to the battery terminals and jumping the 12VDC trailer batteries with my truck start battery. The slide worked perfect every time doing this. This was telling me my trailer batteries may have a low charge state...
Just a couple of thoughts here...
Roy Ken