Hard to see the crinkles and other things on the back, but here's a link that describes

the Southern Black Racer as being black or dark gray. He's probably helping your garden by devouring some of the pests. I have a big racer that lives in my yard

also.

https://edis.ifas.ufl.edu/uw251

The lumps and bumps are probably small things he's eaten that are digesting in his belly. Just look at his head. If it isn't triangular, he's generally not deadly.

Black racers can look very different.

https://srelherp.uga.edu/snakes/colcon.htm

It's a southern black racer. The younger ones have more white on the chins. The irregular body pattern is caused by the snake's underbelly pushing downward at different angles to propel itself forward on the soft grass. The dull color could be caused by crawling through muck or it could be preparing to shed skin,

What Steve said. We see them all the time In our yard. It always makes my day to see them.

We find their shed skin all the time too.

I don't mind seeing them and they usually move pretty fast out of my way but the other day I was knelling on the ground weeding some big pots and I looked next to me (less than 1 ft) and a big one was right beside me. I was really surprised it came right up to me. Needless to say I probably won't weed kneeling next time.