The Time Travelers sounds exactly like the movie I have been looking for. Thank you. Thank you. Thank you. Now, if I can just find a copy of it....

"But in the last quarter, Melchior brings The Time Travelers to a remarkable ending where the time travelers return through the portal only to find the world moving 100 times slower than they are and watch themselves starting the whole process off again, then traveling through the portal a second time and becoming caught up in an endless loop. It’s a wonderfully imaginative touch. There’s something about this that is pure science-fiction, it’s a tiny gem of what the genre is all about when it is at its best, and something quite delightful to find in a B-movie like this.."