Sounds like a sticking thermostat. Had the same problem a couple years ago. Put a brand new 160 degree thermostat and never had another problem with it.
95 yj, 4 cyl, auto trans, 4 1/2" Rubicon Express extreme duty lift,
33" BFG Muds, 4:88 gears, Detroit's front and rear, Dana 44 rear axle with disc brakes, heavy duty Dodge NP231,SYE, MORE sport cage. Blue Jeep Club Member #61