Car stops accelerating for a few seconds.

I have an Opel Insignia 2010 Sports Tourer with a 2l diesel engine. I'm not really that knowledgeable about the mechanics of a car so I don't have a clue what could cause this. I'm trying to get some infos on the damage (if there is any) before bringing it to a mechanic so I have a basic idea of what it will cost.I have two issues that i think are tied together. The first is that the car starts shaking when giving it just a little bit of gas at 1500 rpm and below. By shaking I mean it's as if I played with the gas pedal (press, let go, press, let go, ...). If i give it more gas or if I'm at a higher rpm there is no issue. The other Issue happened twice so far. The car would lose acceleration at around 80kph for a second or 2 and then would return to normal. Do any of you have any Idea about what could cause this?Thanks! via /r/cars http://ift.tt/2sVcIpv