Issue with Ruud heater needs a new thermostat or limit switch

My heater (model RCFL-HM3617CC) is not staying lit all the time it is on. I will start at the start of the season. I turned it on like normal and it would have a cycle of turn on running (blowing out hot air) turning off then repeat about three times and then stopping. It was always three times so I just dealt with it thinking I just needed to change the filter but kept forget about it. Fast forward to Monday 12/3 I was getting ready for work an was thinking it is colder then normal in here(I set the heater to 68) look at it was at 56. I was running a little late so I had a friend turn it off and ordered a filter thinking that was the issue. I then found a filter and changed it out kicked the heater on at 60 degrees run just fine thought nothing of it until it got down to 56 again without the heater kicking on. Looked at the window on the top panel and the green light was on. getting to 12/7 I heard it start up and went to look as I had been seeing the flame until it kicks to where it blows heat then the flame goes out. There are times when it would stay on and warm the house to 61 (I still have it set at 60) and now it is back to not having a flame. There was also a flashing yellow little that was giving a code for air but I just replaced the air filter so that make no sense