Camera plunges down while using keyframes

This is my very first time using Blender so apologies in advance if I don’t have the right terms. I’ve been following a tutorial to make a logo (tutorial here: https://www.youtube.com/watch?v=yMZ5g_nWqvs )

It’s been fine up until the animation section, where I am adding movement to the camera using keyframes. (about 23:52)

I can set the initial keyframe and add/remove them, but unlike the tutorial, in my version the camera’s default position seems to be wildly off, somewhere in a faraway part of the plane.

Is there an easy way to reset a camera to a set “default” location?

And using the keyframes, why doesn’t the camera location stay at the place I position it at a keyframe?

I’m so sorry if this isn’t clearly explained. Maybe it’s better to show it by ASCII art. Camera position is the X, Keyframes the Y:

          *                                  *                  * 
           *                                                   *
           





              ***********************  **************

Timeline 0 --------------------------------------------------------- 100 frames

All the upper keyframes are ones I’ve manually entered. I’m wanting to shift this lower line up to something “normal” and ideally have the keyframe that I set at frame 1 remain “sticky” until the new keyframe is entered. Somehow my default keyframes are just wildly off.

I hope this makes sense and if I’m duplicating a question that’s already answered I’m sorry – not knowing how to exactly explain this has meant it’s very hard to search or really know if my answer is already staring me in the face.

Blender is just STUNNING, by the way. Cannot believe how powerful it is and how easy (overall) it is to make animations and graphics.

Thank you in advance for any help!