Why does my brain work at 4.00am?

My brain snoozes through most of my day, not involving itself with whatever I am doing. For some reason at about 4.00am this morning a thought arrived and crashed about in my head for the next three hours or so. 
The work being done over the last couple of days included opening the lid on the septic tank, thankfully not something done very often. The tank is fitted with a bubble machine that cleans the water before it is pumped out into the drainage system. When its working it is obvious, the liquid in the tank appears to be volcanic from the air being pumped through it, the splashing can just be heard with the lid closed and the pump itself can be clearly heard in the garage. 
So why did I decide, at 4.00am this morning , that it was not working? The longer I thought about it the more convinced I was that there was a problem. Initially I decided that the power had been turned off from the pump; by 7.00am I knew that the whole system was broken and it would be hugely expensive to sort out.
It was light by then so I got up to try and patch it up before the experts can come and rectify the problem. Strangely at that time the world is very quiet and the pump in the garage and the splashing could be clearly heard, everything was working well. Except my brain that had been on overdrive for the previous 3 hours.
Blip is Sunday sunrise with a promise the rest of the day will be better.