1989 420 sel
 

hello,
i have a 1989 420 sel. i love it! it has about 220,000 miles and runs super except for....this is where i need some help.
every now and then the engine shuts off while i'm driving. yes, it's scary. i pull over and wait about a minuteor two then i can start it again. i believe it happens more when it hot outside (about 95-100 degrees) but it also has happened when it's 70 degrees. i'm thinking it's a relay switch butreally have noidea nor does my mechanic. when it happens i do have electrical but that's all- everything else just shuts down- has anyone had this problem or have any suggestions?