Maintenance for the week of October 12:
• PC/Mac: NA and EU megaservers for maintenance – October 12, 6:00AM EDT (10:00 UTC) – 8:00AM EDT (12:00 UTC)
• Xbox One: NA and EU megaservers for maintenance – October 14, 6:00AM EDT (10:00 UTC) – 9:00AM EDT (13:00 UTC)
• PlayStation®4: NA and EU megaservers for maintenance – October 14, 6:00AM EDT (10:00 UTC) – 9:00AM EDT (13:00 UTC)
Holding Q will open the radial menu and let you select an item. Let go of it and the selected item will show in your "slotted item" icon. Pressing Q once (without holding it and opening the wheel again) uses whatever item is currently slotted. Potions have a cooldown timer, so you can't use one again immediately .
It's just one of the annoying control schemes ZOS came up with to accommodate the limited trigger availability of console controllers. Much like the access to only 5 skills at once.