Electrics W461er G

Servus my loved ones, I have a little problem with my 91 wolf. Every now and then the lighting flickers during the ride – not inside, radio goes on normally, but the pig throwers flicker in the front. I can’t say it with the rear lights. It usually occurs after about half an hour of driving. It then flickers for 3 seconds and then goes back to normal. You have to say that it is already very cold, but whether it can be because of it …? Maybe you have ideas. Felix