The Roman generals, as well and the ancient Greek ones, were both military leaders and soldiers. They had to encourage their army with yells, speeches yet they had also to prove themselves in battle. Of course and he wasn't all the time in the front line because as a general had to execute the battle plan, raise the morale of the army, order retreats, flank maneuvers, send reinforcements etc. From the ancient written sources, we do have instances of Caesar's personal involvement in Battle. For example:

Caes. Gal. 7.87-8: Caesar sends at first young Brutus, with six cohorts, and afterward Caius Fabius, his lieutenant, with seven others: finally, as they fought more obstinately, he leads up fresh men to the assistance of his soldiers. After renewing the action, and repulsing the enemy, he marches in the direction in which he had sent Labienus, drafts four cohorts from the nearest redoubt, and orders part of the cavalry to follow him, and part to make the circuit of the external fortifications and attack the enemy in the rear. Labienus, when neither the ramparts or ditches could check the onset of the enemy, informs Caesar by messengers of what he intended to do. Caesar hastens to share in the action. His arrival being known from the color of his robe, and the troops of cavalry, and the cohorts which he had ordered to follow him being seen, as these low and sloping grounds were plainly visible from the eminences, the enemy join battle.

 Plutarch, Parallel Lives 18.3: Here, after he had collected and arrayed his forces, a horse was brought to him. "This horse," said he, "I will use for the pursuit after my victory; but now let us go against the enemy," and accordingly led the charge on foot.  After a long and hard struggle he routed the enemy's fighting men, but had the most trouble at their rampart of waggons, where not only did the men themselves make a stand and fight, but also their wives and children defended themselves to the death and were cut to pieces with the men. The battle was hardly over by midnight.

Plutarch, Parallel Lives 20.7-10. They routed his (Caesar's) cavalry, and surrounded the seventh and twelfth legions and slew all their centurions, and had not Caesar snatched a shield, made his way through the combatants in front of him, and hurled himself upon the Barbarians*; and had not the tenth legion, at sight of his peril, run down from the heights and cut the ranks of the enemy to pieces, not a Roman, it is thought, would have survived. As it was, however, owing to Caesar's daring, they fought beyond their powers, as the saying is, and even then did not rout the Nervii, but cut them down as they defended themselves; for out of sixty thousand only five hundred are said to have come off alive, and only three of their senators out of four hundred.*

Furthermore, in 75/74 B.C. Caesar was captive of the Cilician pirates and held him for ransom. After the ransom was delivered and Caesar went free, he managed to raise a small naval force (as a privatus, he held no public or military office) and attacked them in the harbor of Miletus. [Source: Luciano Canfora, Giulio Cesare. Il dittatore democratico. Plutarch, Parallel Lives 2]

Personally, i do not know how many times and if Caesar fought someone individually but for sure he participated in battles among his soldiers in numerous times. I'm sure that there are many examples besides the ones i mentioned. Thank you for your time. I hope i somehow provide you with an answer!