Evan of Saxony:
I have never played the Austrian side, but you mention it is June 1805. My expectation is that come September, you will be in a world of hurt. It is going to feel like the Tsunami rolled over you. You must be playing the larger of the two Campaign games which begins with the French army on the coast. They likely remained encamped through Spring since moving in Winter is very costly. But by June they are likely coming across France to hit you.
If I were you, I would be putting your forces into the strongest defensive positions possible quickly and then letting them entrench. You also need to be increasing the fortifications back from Ratisbon, to munich to salzberg, Linz and Vienna. Watch your flanks since the French will likely try and envelop your position in Bavaria. Try to bloody Napoleon as he hits your prepared defenses, but realize that you will not hold him and will need to fall back in an ordered way, ready to jump on any French units that get ahead of the main force.
This is a long struggle. You will not win the war in 1805 because your army has not gone through enough improvements to be able to compete with the French. Your strategy should be to with draw in tact as much of your army, grabbing a few isolated victories which can give experience to your generals and troops and hopefully increase the skill of your leadership cadre.
Your goal should be to retain a meaningful fighting force, reorganize with the best leaders in command, modernize your army and have a striking force which can damage Napoleon in 1806-1807 when he is engaged with the Prussians and Russians. In other words you want to stage the equivalent of an 1813 Allied strategy, but much earlier. One option might be to withdraw your forces to Budapest, sign a treaty with France and then start a war with the Ottomans in order to refine your force and upgrade your leadership. After you have sharpened your army against the Ottomans, you can choose the proper time to hit the French.