Subaru keeps shutting off while driving - 1997 Subaru Legacy

run fault codes
check for broken timing belt

If this vehicle has a stand alone ignition module, that is more than likely the culprit. Change the igntion module and the problem should go away.

if it is an automatic, whitch i assume it is, locate and test the shift solenoid.

Get a piece of wood like a wedge. Drive it in but be careful you do not rip out the rubber seals. De-icer can work if you buy a few cans. Hot water will also help if you keep putting it on before it freezes back up. Don't feel bad cause it happens a lot over night from dew and moisture. I keep a piece of word in the back of my truck for the same reason when I am up north.

Worn valves.

maybe you should have a look at your air flow sessor

check fuel pump and relay

You could try to install the fuse under hood on passenger side that is used for short towing. Should release the rear. Good luck.

check your fuel filter