Emissions warning light

Temperature gauge rose to 90 this morning before starting engine. But prior to this event, I had an issue in mid January, engine wont start, none of the mechanics could find what was wrong but we had to use easy start to start then engine works, did that for weeks and then it suddenly one day in March started working on its own. Just last weekend I noticed its hesitated and following day back to non start and but now with the temperature gauge constantly on 90 before moving at all. The temperature gauge was moving back and forth at a time and the engine is certainly not itself