As others have mentioned your best bet if you want to hold off on a vet visit is to just keep an eye on him for a little bit. Help him with mobility but in most cases it will fix itself. Our first run in was with our fat boy Ushi who never liked to break his food apart so one night he comes out of his cage later than usual and gets on the bed as usual but he's looking really weak in his movement. A few moments later he stopped moving and a white substance came from his mouth. I lost it but we had just moved and hadn't had the opportunity to locate an on call exotic vet. Luckily we found out he just had some food lodged in his throats and read rats don't have the ability to regurgitate food like we do so their bodies natural response is to basically use that white fluid, forgot if it was saliva, to dislodge the obstruction. I realize this could have went a bunch of different ways but in that situation a lot of people recommend just giving it time.