Can you give us a bit of a service history to the car? Are you up to date on the service schedule as listed in your owners manual (or Haynes & Bentley books)?

I would strongly recommend completing chapter 1 of the Haynes service manual (available at just about any autoparts store). Also, I'd be looking for electrical issues as previously mentioned.
1. Worn spark plugs.
2. Worn spark plug wires.
3. Worn cap and rotor.
4. Ignition coil failing (intermitent breaks/opens).
5. '82-87 wiring harness falling apart.
6. Inductive pickup sensor in distributor failing.

Transmission issues sound like low fluid level. Follow the instructions in your owners manual and make sure that it has enough transmission fluid (DEXRON III). If you don't have the owners manual, the steps are listed in the following link:
http://www.brickboard.com/RWD/index.htm?id=717912

I would strongly encourage a good cleaning of the IAC Valve and the Throttle Body, followed by setting the idle at proper spec if possible. Here are a few past posts that may help you on your way:
http://www.brickboard.com/RWD/index.htm?id=710885
http://www.brickboard.com/RWD/index.htm?id=708363
http://www.brickboard.com/RWD/index.htm?id=706243
Wiring harness info
Dave Bartons page on Volvo 240 Wiring harnesses

God bless,
Fitz Fitzgerald.
--
'87 Blue 245, NA 229K