Mine did that once and it was the ignition switch.
#1
98 VR6
I recently did my timing chains, after I re-installed the engine it cranked over fine, ran, re-mapped itself, but my battery warning light came on.
Turns out I was an idiot and didn't connect the alternator to the starter properly. Switched that around. fixed.
Now when I start the car it starts up fine, but the damn starter motor keeps spinning with it.... is it a screwed solenoid? bad starter altogether? am I a bigger idiot and still didn't connect it right? Did my previous fu*k up screw my starter? Help I have to go to work soon!