My 1994 Volvo 850 GL has recently begun to halt the engine at seemingly random intervals. Some backstory: Since I bought it second-hand in 2013, it's had an intermittent problem where when I start the car back up a short time after having used it, it'll immediately die, and refuses to start back up unless I let it sit in neutral with the power turned off for 1-2 minutes. This occurred pretty rarely, maybe once a month or so, and was never an inconvenience since the car would start back up and run perfectly again after waiting a few minutes.
However, the last couple of weeks, this has started happening while the car is running and in motion. While driving a friend home last weekend, the car suddenly stopped responding to the accelerator, all the dashboard lights lit up, and the car rolled to a stop. I first attempted to start it back up immediately, being a little panicked to be stopped in what was essentially the middle of the road. It didn't work, so I flipped on my emergency blinkers, waited two minutes, and it started back up without so much as a cough from the engine.
Yesterday, the exact same thing happened on my way home from work. I was doing 80kph, and suddenly the accelerator stops responding, all dashboard lights light up, and the car is unresponsive until I let it sit for a few minutes.
My first suspect during these stops has been the battery, but all electronic systems such as the AC and the stereo keeps working, and there are no other signs of excessive battery use that would "out-drain" the charge provided by the alternators.
My father, although not a car mechanic, has experience with Volvo 850 maintenance and repairs, and has told me it might be the petrol filter, or the lid that keeps the spark plug cables in place on the engine block. However, he's unable to help me start tinkering with the car until at least the end of this weekend, so even though I know the basics of what components are and what they do, I don't feel confident enough to start messing with the car on my own. I got a severe backlash on my taxes this year, and have very little money left over, let alone for a mechanic or a garage. This is my only car, and I need it to run for at least another half year to a year, when I've saved up enough to replace it.
What could be causing this problem?