Yeah I'm the same when under fire actually. Any tips? Not too bad in my MkII. Have the highest win rates in various med tanks.
theres no shame in backing off ,especially if you cant see whos shooting at you - use all available cover-including dips in the ground and dead tanks - if you are returning fire while being shot at yourself try to let the reticle close fully before firing, unless the target is 10-20 yards away, it will increase the chances of a lifesaving kill shot. Also-before the match starts -check to see if there is arty - try to keep moving if there are arty in the other team-even if its just back and forth 5-6m ,its enough to put them off.
If you have multiple targets -try to prioritise - if theres a tank you can finish in one shot, thats one less gun shooting at you and your team
If you are trying to reset a base cap with multiple tanks in the cap -shoot each tank once and the cycle through the lot-as you damage them,they lose the cap points they have accrued
Also in medium tanks, look for the opportunity to flank an enemy thats pinned down behind an rock or building -use your speed to get to the side or rear and pile on the misery