Why is my console shutting off and resetting?

I have owned a super famicom for about 2 years now and it used to work fine, but recently it has started to get into some kind of reboot loop in every game. It starts with grey horisontal lines appearing and blurring the screen a bit, but the game still works and there is sound and colours behind the lines, but after a while the lines get very noticable and the console resets, but the lines are left and the resets happens more and more frequently.

The console will sometimes work fine for over an hour, but sometimes the lines appear immediately.

I have tried cleaning both the cartridges and the cartridge port, but it doesn't seem to help in the long run, the problem is the same on all games I've tested.

If somebofy knows what might cause this problem, and knows how to fix it, I would be very grateful:)

The serial number seems to be “SM11834888” if that's of any importance.