Assuming you have been diligent with your transmission flushes (?), I would suspect your PNP switch first as your first set of symptoms sound exactly like a PNP issue. Part is not expensive, $80 t0 $110 at FCP Groton. If you want to DIY, excellent instructions on Volvospeed.com. Probably about a 2 hour job if you take it to a shop.

However, first try 'raking' the shift lever (with engine off) back and forth 15 times. This will often clear the contacts and clear the problem thereby identifying the PNP as the culprit. The problem then may not come back for quite a while if it was just gunk on the contacts or sooner if the switch is indeed worn. If a code has been set (check engine light on), and the car now shifts normally, you will need to clear the code.

One other reason I would suspect the PNP is that it tends to act up in the winter when things are cold and damp
--
96 850T, Bilstein HD, IPD swaybars