I have an odd situation. The electric window on passenger side is non operational from switches on passenger and driver door after car has been sitting idle for a few weeks and is cold. The driver window switch works but is slow and sluggish. After the car is started and been running for 15-20 minutes the passenger window starts to work and the driver window is no longer sluggish and "wakes up." I keep the battery on a tender while car sits in garage. Could there be a lack of voltage going to the switches until engine has run for 15 minutes? Any suggestions as to what part of electrical system needs to be addressed so that passenger window is operational when cold?

Thanks in advance for suggestions.