No surprises here...most common is to start after a touchback (own 25), and it's really rare to start inside your own 10 (since those often become touchbacks). There's also a big spike in plays at the goalline because goalline stands happen slightly more often than plays from, say, the 6 yard line.

It is a bit interesting that there is a slight bump for most multiples of 5 yards. I'm not really sure why. It could be an impact from many penalties being multiples of 5 yards. It could be something like ref spots just being slightly biased to 5 yard increments. It could be that first downs are 10 yard increments and they start at 25 more often than other locations so it is biased by that. If someone has a better idea please post in the comments because I'm curious now.