It may be that she has an infection or irritation in her ears causing the head shaking and pacing. Picture your ears itching or aching and not being able to do anything about it.
Check inside her ears for signs of any discharge, redness, irritation, an embedded tick etc. Ear mites, allergies, ear infections can all lead to head shaking due to irritation in the ear area.
Senior dogs can also have a problem with their balance center in the ear leading to a head tilt and sometimes drunken looking walking or even vomiting much as if they were motion sick.
If the ear just looks irritated red or swollen this may be due to allergies. You can consider trying some plain Benadryl for tonight and see your vet in the morning.
A common low dose is 1mg per pound of dog every 12 hours. If you choose to use that please read here about cautions just close any pop ups so you can scroll down the page to read the info
http://www.petplace.com/drug-library/diphenhydramine-benadryl/page1.aspx
Even if you have ear meds on hand there are important things to know before deciding to use a medicine in a dog's ear.
You need to know if this is an infection or an ear mite problem as they are treated differently.
You need to know if the ear drum is perforated or not as most over the counter meds are not safe if that is the case.
You need to know if this is something that will clear up with topical meds, require oral meds, or is related to a problem with allergies or a thyroid problem.
If you know the problem is an ear infection and that the ear drum is not perforated then there are some things you can use.
You can see if your local pet supply store carries Zymox with cortisone or find it online. I've had good luck clearing up infections with that. You can read about it here http://animalpetdoctor.homestead.com/Zymox.html This site goes over ear infections and has another ear cleaner mentioned that had good results http://www.dermapet.com/articles/art-03.html here is just the product info http://www.dermapet.com/prod-09.html Ear infections are a common symptom of allergies in dogs. You can read about allergies and dermatitis in dogs here http://www.lbah.com/allergy.htm
http://www.priory.com/vet/vetatop1.htm Dogs can develop allergies to foods, and to inhaled items, and contact allergens such as rug cleaners or chemicals including lawn chemicals or even flea bites. You might want to try a different dog food that has no ingredients the same as what you feed now. A Fish and Potato diet works for many dogs for example.
Dogs can also be prone to thyroid problems which can trigger allergies and infections.
I'd plan on seeing your vet about this.
If your dog might have gotten into anything toxic, appears dehydrated (see if a pinch of skin over the shoulder blade stays stuck in a tent form or flows back down normally when released), has a rectal temp over 103.5F (normal is 100.5-102.5 Fahrenheit or 38 - 39.2 Celsius ), has gums or tongue that look white, blue, gray or yellow tinted where they are normally pink, has a slow color refill if you press on a pink area of gum or tongue, is not breathing well, or is becoming lethargic and non responsive to you then you may want to get the dog in to see an emergency vet tonight if one is available in your area.
Hope this helps you!
Dog Expert:Rescue, Train,Breed,Care
30+ yrs dog home vet care & nursing, rescue, behavior&training, responsible show breeding, genetics