06 Nissan Pathfinder electrical

I have a 2006 Nissan Pathfinder when we bought it
we were told there was nothing wrong with it and
then I started spitting out transmission fluid so we
had the transmission rebuilt (it needed it) it would
run fine for a minute or two and then all of a
sudden it either won't shift out of first gear or it
stays in 3rd gear so we replaced the
transmissions computer so now I have a rebuilt
transmission but still having the same problems
and I think it may be something electrical because
while I'm driving down the road everything
electronic will shut off all the dash gauges the AC
the lights everything shuts off I have to turn off
the car and restart it and then everything's fine I've
checked the connections from the fuse box to the
alternator check the battery just wondering if
anybody has any idea of what this could be