Intermittent boiler problem

I have recently noticed an intermittent problem with my boiler. When the cental heating is on the boiler cuts out and a red light on the boiler comes on. However, when the re-set button on the boiler is pressed, it works fine again. Please advise as to what may cause this problem. I have had a plumber look at it and although he could not find the cause of the problem felt it was not something to be concerned about. I welcome your opinion.