Does this happen to anyone else?

I don't think this is necessarily autism related. It sounds like you simply have an efficient and healthy immune system that is in good working order - like a child's!.  Your immune sytem responds to the threat by unleasing an inflammatory response, manifested as symptoms. The symptoms are good, even though they are perceived as horrible - they are the by-product of a healthy immune system. The bugs are cleared out of your system quickly,  and so  there is a prompt return to health, instead of a sluggish and prolonged response - the signs of an inefficient immune system.

You say you eat a healthy diet and look after yourself - this will facilitate a healthy immune system.

Many people don't look after themselves when they are sick, which only keeps them ill for longer. My immune response seems similar to yours: on the rare occasions I get ill, I will suddenly feel tired and headachy. If it is a stomach bug, I am sick only a few times, and two hours later I am fine!. This happened once when a severe bug was going round - other people were wiped out for days! My illness only lasted a couple of hours.

Everyone, though, has a different immune response, and healthy immune systems all vary. By sleeping when ill and avoiding work, you hasten your recovery.

I know this is three years old but stumbled upon it as it a"related" post to a current one I was reading.

I quite often get ill and recover very quickly,I work outside all the time,my work is very manual and at age 55 I weigh nine and a half stone.I do however smoke a lot(addiction) and eat fairly well although don't enjoy fruit and tolerate vegetables. 

My doctor told me I am one of the fittest 55 year olds she has met.

I usually get summer and then winter colds. They start off quite pronounced but then settle with little effect but they linger, If I feel unwell I eat plenty regardless of appetite,I believe eating fuels the body to fight off illness.

I rarely have days off sick and even when feeling very ill I usually go in if I can. I must add that I am not formerly diagnosed with ASD but truly believe I am and always was. 

I know this is three years old but stumbled upon it as it a"related" post to a current one I was reading.

I quite often get ill and recover very quickly,I work outside all the time,my work is very manual and at age 55 I weigh nine and a half stone.I do however smoke a lot(addiction) and eat fairly well although don't enjoy fruit and tolerate vegetables. 

My doctor told me I am one of the fittest 55 year olds she has met.

I usually get summer and then winter colds. They start off quite pronounced but then settle with little effect but they linger, If I feel unwell I eat plenty regardless of appetite,I believe eating fuels the body to fight off illness.

I rarely have days off sick and even when feeling very ill I usually go in if I can. I must add that I am not formerly diagnosed with ASD but truly believe I am and always was. 

I have a related problem and have had it my entire life.

I often feel totally exhausted for unknown reasons and it lasts about an hour.  I recover very quickly after that.