Well, but general relativity teaches us that all coordinate systems (also constantly moving, but not accelerating ones) are equally relevant. This means that the one with earth as it's origin is as correct as one where with the center of the galaxy (or the sun ) as is every other. So the one where earth moves somehow through space is just as random as any other.
I guess it depends on the sort of time machine. I'm thinking the H.G. Wells variety- a machine you get in or on and it takes you back in time, but to the same location.
Well if you time trivel to "the same location" then that would be in space somewhere because the planet had moved on.
In films you travel to another location, which is where the earth is now/then.
Also, we rocketeer forwards on this spinning globe, so if you time travel 6 months, the planet will be going in the opposite direction (and also be on the other side of the sun ofc.) so iven if you move yourself there, you'd get smashed against the planet at high speed or ejected away from it at high speeds probably be killed by the atmosphere if by nothing else.
That's actually kinda my head cannon as to why the doctor in doctor who is so hands on when piloting the TARDIS a time machine that only travels through time is useless because you can't affect history while floating out in space and it's also dangerous if you happen to pop into existence inside a block of dirt the more I think about it doctor who is a pretty realistic depiction of what time travel will be like even with the TARDIS moving air out the way before landing instead of creating a shockwave from TARDIS molecules materializeing inside of atmosphere molecules