Why does my Schnu hesitate to jump & inconsistently squak?

[schnu2005]

My Schnu is 12 years old & will be 13 at the end of September; she seems normal & healthy in every way, but these last couple months hesitates & sometimes refuses to jump up on my chair or bed by me (occasionally when she does jump up she miss judges it, but other times does it perfectly with no problem). Before she had no fear when she jumped on furniture & judged every jump perfectly.

Also recently, she began squaking at me unconstistantly when I pick her up or move her (with the same movement she squaks & does not squak). Every time she squaks I move her legs and feel around her whole body for any reaction or pain with no results (no squaks).

She doesn't have cataracts, joint issues, arthritis, doesn't limb, or anything else; she's seems to be healthy in every way. Even her vet visit this past week verified it.

Could she all of a sudden due to age be afraid to jump up on furniture by me?

Why when I let her know I'm there does she appear to be startled occasionally?

Could pain literally last a minute or less inconsistently?

Could after all these years she be giving me attitude when she doesn't feel like being picked up or moved?

It's scaring me because she's never behaved like this before and I've been her sole caretaker & best friend since she was 10 weeks old. It's also scaring me that I've ran out of ideas on how to help her. She's generally a go with the flow, whatever kinda dog who listens & obeys living to please. Please help; I love her so much. Thank you.

P.S.
Read other posts & couldn't find any answers