SUburban NT32 furnace cuts off after 30 minutes

Upper limit switch makes sense. When i warmed the rig up slowly into the range of room temperature then it worked fine for the rest of the day. Outside temp was upper 50's and the furnace cycled on an off throughout the day.

Then at night it got colder and this morning furnace was running cold.

So, does that automatically mean the limit switch or could it be getting too hot and the limit switch is doing its job?