Engine power loss, sudden, no engine light?

The vehicle listed above is a Sport model, very random, always when car is moving, suddenly car dips forward for a second, engine goes into some sort of limp mode, still on but barely reacts to gas pedal, tachometer zeroes out instantly but other dash readings normal, brakes, steering, A/C, etc., all normal, but No Engine light not any other warning lights or messages, after several of these over weeks' time, I found that I could park, turn off, wait ten seconds, start back up, it cranks and runs totally normal as if nothing happen and tachometer is back on. It'll run good various times, 3-4 days or a week, 2-3 weeks, once even went a month, engine scans show nothing since I can't get to the shop while it's going on. And, more mystery, occasionally one of these episodes it only does the little lurch but goes instantly back to all normal even the tachometer. Has been between speeds of about 25-50mph. Please hurry with ideas.... I'm running out of hair to pull out.