Feedback on overnight parking...

I will be soon taking a trip where it will be necessary for us to stop for the night, only to get a few hours sleep, and then move on to our destination. We will be traveling along an interstate.

My question is how safe is it to stop, park, and sleep in a Walmart parking lot? (I would ask the manager for the OK, and where to park.) I know there is a LOT of discussion on this forum about Walmart parking, but I have not read about too many experiences, good or bad.

I have never done this, so I am not so sure about it, and I have concerns about how safe it would be. Since all we need is to sleep, I think a campground stay for one night would be a waste.

I would appreciate if you could share your actual experience with this, and any thoughts on any place that may be safer.