Trans No Go 95 4x4

I CAN DRIVE FOR 30 MINUTES SOMETIMES 3X THAT, THEN THE TRANS LIGHT FLASHES AND IT WON'T DOWN SHIFT.I TURN IT OFF AND START UP AND RIDE WITHOUT ANY PROBLEM UNTIL THE NEXT EPISODE. IT HAS ACTED LIKE THIS EVEN AFTER FILTER AND FLUID WERE CHANGED.WHAT'S UP WITH THIS BEHAVIOR. Izu3.2