Onboard computer 850er BJ94 spins…

Hello, I am fresh in the forum and have already found a lot of information here. But I have a problem with my on-board computer, to which google has not spit out a suitable answer yet. And indeed the BC spins in the form that it runs for a time well and then falls out without any obvious reason and turns off again and again. It is as if you hit the battery on and off. When the car is standing he sometimes still spins and then it is like if nothing had been. So I think, I could almost exclude a wackler, because he goes back to the standstill. Also the lighting did not go on, and finally, during the ride after a small Ruckler has switched on again. After the following failure, everything was dark again. Could it be a wocker or maybe gets some kind of wrong current. Have the car for 1.5 months and don’t know the previous history. Next, the AI should be able to get out of day-kilometre counters and lamps and since then I wanted to ask myself if the problem is familiar with the BC.