My DD did this too at about the same age. She has never been a good sleeper but 18 to about 23 months was a killer!

While I'm not an advocate of leaving them to scream I found that if I left DD she grizzled for literally 90 seconds then rolled over and went back to sleep. I still wake but at least I'm not getting up. Now I probably hear her once or twice a night most nights which is a great improvement.

Oh, and someone told me recently to remember that eventually they will be teenagers and then sleep constantly! Lol