Excel is responsive, moving the window is not

Hello everyone, I have a problem with my Excel: When I move the window around, there is a noticeable delay (0.5 sec or so). The "inside" of excel works really quick and responsive, but the window movement feels so sluggish.

Before you ask: I don't think that it's the strength of my hardware. Although my PC is a few years old, it's still powerful enough to play all of today's games at the highest setting. All the more so I really wonder why exactly Excel brings my PC to its knees. The only other programs that have such sluggish window movement are Word and PP (=all office products).

I monitored the CPU whenever I try to move the Excel window back and forth and this is the result: http://fs5.directupload.net/images/170217/f8gcmnsu.jpg

The spikes show up whenever I move Excel. Is this normal? A Google search unfortunately brought no results and most people just search why their excel is "slow"...

Does anyone of you have an idea what the problem might be?