i felt the exact same, seems to be the norm, make sure your battery is in good condition and give it a good charge.
Headlights will dim if you have normal bulbs, same when a/c and windows being used, you'll only notice this when parking up.
Doesnt happen often for me but i have an earthing kit (dont know if this makes any difference), HID lights and car battery is in good condition, been through 3 winters and drove it a little, car starts everytime.