Flejm4k

Hi guys, I've been having a weird issue with my ML 320 CDI. I had the car for over 10 years now without any big problems. About a year ago, my instrument cluster just randomly shut off while driving. Firstly the front parking sensors go screaming and then the cluster dies and a second later, they are working just fine. It used to do it once in 1500-2000km so i did not worry about it at all. But nowadays, it randomly just shuts off, sometimes after 200km, sometimes it happens 3 times in a row in one minute and then nothing for another 100km. I also found, that after they go dead, the Cruise Control and the Downhill Speed Regulation don't work. After I turn the car on and off it works fine. Even the buttons on the radio sometimes don't work and after this weird reset, they work. My mechanic did not find anything only, that a negative charge is sometimes lost. Also changed battery about 2 years ago and a rear SAM recently.
Any ideas, what could be wrong? Could the front SAM be damaged or maybe some wiring problem? I have checked most of the grounds I could find and see.
Thank you for any tips.