Straightening out paths

I know I’ve seen this as a topic before, but I can’t find it.
It only occurs once in a great while.
I have an object moving straight from one point to another
and it creates its own curved path.
How do I straighten the path out?

This happens when you’re using a 3D path. Either change it to do a Separate path, or you need to select the keyframes on your 3D path and set the tension to 0. The easiest way to do this is to open your Control Points toolbar and do it from here by selecting the peg or drawing you’re working on, doing a View > Show > Control, and then select the keyframes you want to adjust.