Vamp, This has recently happened to me. It started the Sunday after Christmas when I woke up. When i went to lift my head I got very faint and the room was spinning. It passed and after a bit I was able to slowly get out of bed. I spoke with my friend who has lost a large amt of weight by gastric by pass. she said that when you lose a great deal of weight it can mess up your equalibrium and cause this. I did a goggle search and found gastric by-pass sites that said some GBP suffer from dehydration by not drinking enough water. I realized that I had not been drinking near enough water each day but usually manage to choke down enough each day. Since I was on vacation and out of my usual routine, my water consumption suffered.
Badger has mentioned caffeine and one of the things I love at Christmas time each morning is a good ole cup of coffee. I drank about 2 mugs a day and that is way more than I have had in a year.
Looks like it might be a double whammy for you, too much coffee not enough water or your equaliberium.
This sure has made me make a better effort to get the water in each day.
Do check w/doctor if it continues. Mine went on for about a week but lessened each day and I glugged the water.
edi