1998 and 99 E320 Engine problems

Hello all,

My mom and grandmother both own E320s, (Mom is 99, GM is the 98). We've had a lot of electrical problems with the 99, plus it burns oil, but the 98 hasn't had very many problems until now. Within the last week, both cars' engines died completely while on the highway. I mean, just died and both my mom and grandmother had to pull over quickly to avoid an accident. They're both in the shop now but I was wonder if this is a common or well known problem and how to fix it?

Thanks,
J

definately not normal they are usually pretty reliable. did the shop pull any codes?