They might be mosquito bites. My dog also gets bitten from time to time, usually at this time of year. But then again, she is mostly an outside dog, so spends hours in grass. The bugs bite a lot at this time of year.
Even though yours is an inside dog, when she does go out she might pick up bugs in the grass?
Another thought is -do you use a lot of cleaning products? Especially where she lays down? If so, she might be allergic to these?
You could try: bathing her in an insecticidal shampoo (you could get a good one on prescription from your vet) And you could try putting Benadryl cream on the spots themselves. If they are bug bites, they usually stop itching in a few days. Benadryl cream will last about 4-5 hours, then may need to be applied again.
I was looking in fur last night and her skin is dry....now I put fish oil (o mega 3 ) on her dog food and don't bathe her often. Like the itchy bumps are raised off her skin little and most of itch is going down her spine seems be where bumps are... I give her a benadryl ill daily seems helped little...Guess first week she will go to vet and see what he thinks...