That's a good question. I remember having only a driveway to work in with a similar problem. I put the back of the ramps against the leading edge of the concrete apron. The apron stuck up about 1-1/2" above the asphalt, & acted as a curb that held the ramps from moving with the car. I haven't used ramps inside the garage I have now, only a floor jack & stands, & now I have a lift.
I have an idea you could try, but I never did it myself. Try making a stop for the ramps & use it like I used the concrete apron. If you could get two planks of wood, let's say a 2"x 8" or wider, & lay them on the floor. Let one end of the wood rest against the base of the rear wall of the garage, & the other end at the rear of the ramp.
They would both be directly in line with the ramps, but you would need to cut them to a length that will keep the ramps in the exact location you need to position the car. As you drive onto the ramps, the wooden plank will use the base of the wall to keep the ramps from moving with the car. You have to be very careful that the location on the wall is solid, & not hollow drywall or maybe rotted.
The wall, if it's studs & drywall, (sheetrock) should have at least a 2"x 4" wooden sole plate mounted to the concrete floor or foundation to keep it anchored. It should be strong enough to do the job if you don't hit the ramps at a Duke's of Hazzard jump speed
The only other alternative I can think of, would be some kind of thick rubber mat to use as an anti-skid covering for the metal on the concrete. This might be good enough to try first before getting wood & cutting. I'd wait for a few more responses before trying my ideas, there are a lot of others on here that may have a better idea.
Good luck, Bob