93 325i auto tran 1st & 4th bad

[daddyo8]

OK that's what it seems. Here's the poop.
when I start her up sometimes she slips right into gear fine. other times(more often recently) she bogs down in second skipping first, accelerates to third and stays there at approx. 5000rpm at 60mph.
The problem is sporadic as I described so I don,t see how it can be a band or fluid prob as I just topped off the tranny fluid a couple of weeks ago and the prob persisted. Is there a sensor that might be bad or the linkage?
Has anyone experienced this and cured it?
Thanks