560sl 205K miles

A couple of weeks ago I started experiencing weirdness on startup. About every third or 4th time I go to start up, the starter would fire for qbout a 1/2 second, then hesitate like it didn't have enough power, then the car would fire right up. Now it does it every other time. Just sort of hesitates like it's seizing up or something then it's jump to life. No weird noises like a bad battery or anything like that.

I'm hoping this isn't a chain symptom or something seizing up? How would you go about diagnosing?

Thanks.

J. Boggs