What version of Premiere Elements and what computer operating system?
Generalizing what you are describing is the after effects of trying to add a file to an existing Timeline.
In the simplest cases, this issue can be avoided by holding down the Alt key (Windows) of the computer main keyboard as you make the addition. In certain instances, blocks of clips may need to be Grouped before addition to the Timeline. What needs to be done depends and what can be done depends on the complexity of the Timeline content structure.
This online video tutorial Premiere Elements: Arranging clips on the Timeline using modifier keys | lynda.com - YouTube will give you overall concepts on arranging Timeline clips with keyboard modifiers (Alt or Ctrl). The video tutorial was created with an earlier version of the program, but the concept are there.
Please consider and give more details.