Problems when grab and rotate objects

I’m totally a greenhand in Unreal, actually in all engine, and I’m not a English native speaker, so please watch the video I updated carefully, cause I dont know how to convey my problem more specificly. I be more than appriciate that if you do so.
When I picked something up, without doing anything, it will just rotate all by itself. The worse is, when I try to rotate it, after I release my “set to rotate” button, it will rotate like “Oh My God”.
Pleaseeee help me to deal with it, I’m really bothers for this for a whole day!
Anyway, or you may so kind to tell me how to achieve my purpose: When I see a object, click Button A I could pick it up, it will appear to at the right bottom of my screen. If I click button B, it will appear to at the middle of my screen,and I could rotate it with my mouse to check it out, if I release button B, it will go back to the former position on the left bottom of the screen. And if I press button A again, I’ll just simply throw the object away.

Here is the Video:

Here is my character blueprint:


Have you tried constraining the rotation of your mesh in the physics settings (it’s under the tab named “Constrains”)? You can define there on which axis the actor can move/rotate on.

Hope this helps you a bit.