Loss o power

[DeeBeka]

I have a 1997 Corsa and up until now it's been perfect but a couple of months back as I was driving along it suddenly felt like there was no fuel getting through on the car, it just wouldn't accelerate. It eventually cleared and was fine. Then it did it again this morning. Car started perfectly first time and I had been driving or about 5 mins when suddenly, although the car was moving forward, there was no acceleration if you know what I mean. It made a funny noise too, like I was driving over grilles in the road and when I slowed at a roundabout it felt like the car was going to stall, it didn't though. After a couple of minutes of this it then returned smoothly to normal like nothing had happened. No warning lights came on in the car though I did get a strong smell of petrol for a moment. I went to the dealership and have got it booked in for a diagnostic test on Tuesday but want to know if anyone knows what the problem is.