Car is a 1999 Chrysler Cirrus auto trans with 130k miles. Recently (last couple weeks or so) customer shows video evidence of check engine light flashing for just a second before turning off, says it happens only recently within the last couple weeks or so and often enough to be of concern, tells me it's random doesn't matter day or night, cold start or hot, on highway or street. I have yet to be able to replicate the check engine light flicker, and when I scan the car. (Shop scan tool) No codes whatsoever. Interesting enough when I drove the car yesterday on highway, the rpm went from 3k at 75 mph to 0k rpm car in slow decel, with me not being able to accelerate for at least 10 seconds, brakes and all the lights and radio still working so I turn on hazards ca and then all of a sudden the engine roars back to life and then I continue cruising down back to the shop. Trying to find this online with no luck, not to mention this is a hazard if it happens again. 

A lot of work done prior to this car; suspension work, head gasket, injectors, coils, fuel pump, o2 replaced, vacuum leak, egr cleaned, gas cap replaced, coils, alternator, starter and trans flush, and a fresh battery all within the last 6 months or so of history I could find. Already inspected and everything seems to be in order. Impending engine failure? Or some wack electronic stuff? Customer already decided to junk the car after I told him about what happens on the test drive but I'm just curious if this is something that anyone has come across before?