out of habit
from habit

From long habit, Sean held her back while he got on first.

I'd hoped he'd kept his eyes open from old habit.

Between them they made a reasonable job of it, quick in response to each other from old habit.

More from habit than anything else, Joe led the way with first squad.

They often spring from the same impulses and habits of mind.

He cleaned the game carefully, working from habit without thinking.

More from habit than for any other reason Leonard turned the handle of the door.

But he considered the possibilities of escape only from habit.

From long habit he let in his clutch without argument.

He heard a pheasant call and almost called back from habit.