Hi! My DS had to be Ergo'd to sleep when he was 6 months to 10 months old and then we switched to having to be driven to sleep. He always needed to be distracted or moving to fall asleep for naps. Night time has always been pretty fine.
When DS was around 13-months-old, I had the idea to try to nurse him in my glider - that's motion, right?! I totally didn't think it would work because I'd tried everything and he would always just try to get off and not relax, but it actually did work this time and he's been napping that way ever since which has been AWESOME! And it's a neat little routine that we've started and I can tell now that he actually likes it and longs for it. We used to try to nurse laying down in bed, but I think it wasn't distracting enough for my DS. What I do now is nurse him in the glider (somedays he falls asleep in 10 minutes, other days, it's 30 minutes) and then when his eyes shut, I transfer him to the bed and lay down with him while he finishes nursing (another 2-5 minutes) and then I pop my nipple out when he's crashed. If I transfer to the bed BEFORE he's fallen asleep, he will always roll over, pop up and want to get off the bed and play. So that is key for us - him being asleep before we nurse in bed. I also sing to him when we're on the glider.
Being able to nap like this has made life so much easier. I actually get a break during the day (outside of my car) and when we go out of town, I don't have to borrow a car or walk around in an unfamiliar neighborhood! To me, it seems like the key was that he was looking for something more routine and not in the car and I was good at finding something that distracted him enough.
Who knows if something like this could work for you, but it just might!
Oh, one more thing... in the beginning, my DS would sometimes try to get out of the glider, but I was very firm about telling him, "Sorry sweetie, we can't get down, it's time for night-night." I didn't budge on that ever. Of course, he would flop himself around sometimes and get upset for like 2 seconds, but I'd just offer him the boob again and he'd fall right asleep.