1992 Mercedes Benz 300e stalling

Electrical problem
1992 Mercedes Benz 300e 6 cyl Two Wheel Drive Automatic 250k miles

This just started happening. I drove the car for about 10 miles on the freeway and dropped off a friend. Car ran great as usual. On my way back about half-way, I stepped on the gas and had no response. I assumed the engine stalled so I started making my way over to the shoulder to check it out. I made it to an offramp when I thought maybe I might have bumped the shifter into nuetral. It wasn't but I shifted to 3 and continued back onto the freeway and made it the rest of the way home. I turned into our apartment complex which has 3 speedbumps. After each bump it died when I stepped on the gas. It continued the next day. At the same time I could hear a buzzing at the right rear that seemed to go up and down with the accellrator and stop when stalled. Another unusual thing I noticed was that the oil pressure needle which has always moved to high when applying gas and dropped down at idle, stayed in high position at idle. If the pressure is already high, can stepping on the gas cause overpressure enough to stall? Thanks for your help. Your site is a breath of fresh air compared to all the others.