I know everybody does it, and I know there is an inyan to eat dairy, but is there an inyan specifically for eating cheesecake on Shavuos? And if so, where does it come from?
Nitei Gavriel Shavuos 29:1 note 1 mentions from Kovetz Bais Talmud that in the times of the second Bais HaMikdash they used to eat on Shavuos (לפתות מלחם ומלח (חלב. This sounds a bit like cheesecake to me.
No. Cheesecake is just delicious.