Hmmmm... if by several times you mean more than 5, and on some of those occasions you chose a Mage/Sorcerer protagonist, and you feel comfortable with the spell system, a Sorcerer
might be possible for your first solo.
No guarantee though, and not what I would recommend.
Soloing and Partying are two different ball games. Encounters you thought difficult with a party may become easier with soloing, encounters you thought easy with a party may become harder with soloing.
Since this is your first time soloing, I would rather recommend the Fighter/Mage first. It's more forgiving if you make a mistake. A mistake made with a Sorcerer will punish you severely in the long run.
Some tips when soloing... ...
1) If you are in Chap2-3 and are low-level, walk around Amn only in the daytime. If it is night, enter the nearest inn and rest.
2) Obtain your protection spells ASAP. Do not bother waiting for them to drop as loot. Important spells to get include, Invisibility, Mirror Image, Stoneskin, Spell Immunity, Mislead, Protection from Magical Weapons, etc... ...
3) Web + Spider Spawn will tide you over most of the early battles. Greater Malison + Emotion is another wicked combo. When you can cast Spell Sequencer, GM+Em+Slow is a deadly combination.
4) Trademeet is every soloist's dream. Easy to do, plenty of XP, plenty of cash, and some of the best items in the game.
5) De'Arnise Keep can get hairy for a soloist. Consider postponing it for a while.
6) Copper Coronet is a good place to get XP in Chap2. The second half of the quest however, can be postponed till you gain some levels.
7) If you can bear the inconvenience of not casting spells in the open, don't pay the Cowled Wizards. Wait until you become of a sufficiently high level and attract their attention, proceeding to kill all of them squad by squad( 6 in all), day by day. Otherwise, just pay them 5000 gold.
8)
DO NOT ENTER THE PLANAR SPHERE UNTIL YOUR MAGE'S LEVEL IS 15+ Feel free to ignore this though... if you want a challenge.
9) The Graveyard District has many small quests and tombs to explore. Be careful though.
10) Umar Hills has many good sources of XP in the town itself. The main quest however... can wait until your Fighter's level is 13+
11) Windspear Hills can wait until your Fighter's level is about 15+
12) Cult of the Unseeing Eye. Only two ways to go about it. Buy the shield and go there ASAP. Skip the shield and wait until your Mage's level is about 15+
13) When your reputation is 12+, go talk to the Paladins in the Noble Order of the Most Radiant Heart.
Etc... ...