85 190e intermittent electrical problem

when driving the car I lose what appears to be all electrical power for 1 to 3 seconds (loss of all gauge indications, indicator lights, ignition)
if power is off for a short period, the car restores itself; if off longer, I need to restart the engine.
I checked all visible connections on the battery, fuse and relay box; all are tight. (I did not check the ignition switch, yet).
Most times I can drive the car with no problem, however yesterday it happened three times within a few minutes of each other; and then was okay to get back home.
Any ideas?

Thanks for the help.
Michael