2002 VW Passat V6 engine warm starting trouble

the car start good when cold, But after running 45 minutes to work then turn it off and come back in 2 hours I have to crank the starter 30 seconds or more before it starts and runs rough then in a little bit is smooth out.

Car has 155,000 miles and just installed a new timing belt at dealer. It started hard before timing belt replaced.

What could be the problem? thanks

low compression comes to mind. When it is cold the rings and cylinders are tighter. As it warms up the fit changes. How is your oil consumption by the way? When were the valves last adjusted? poor valve adjustment resulting from wear can contribute to this problem as well.

Have you had any CELs? (Check Engine Light)