Someone with a little more knowledge will soon chime in, but in the meantime I'll provide my .02
You don't mention whether the problem always happens or whether it's intermittent. I'll guess you've already checked your battery connections. It wouldn't hurt to make sure ALL connections are tight, not just on the battery. Check both ends of the ground cable, as well as leads to starter.
You can also try jump starting it with your car after you've run the bike and see if it's still slow to start when hot. If it cranks right up, you can more than likely rule out the starter (unless it's an intermittent problem). If not, could be the battery.
Whatever you do, don't start the car while it's hooked up to your bike.
Last edited by BlazingSaddle; 11-13-2016 at 02:37 PM.