I running 2-2-2-4 wire from a 100amp breaker from the main panel. to a 125amp sub panel. it's going to be a 105ft from main panel to sub panel. Just making sure my wire is right for the job
If your wire is copper then you have properly upsized for a long run and you should be just fine if you are not fully loading the circuit.
The voltage drop calculator here recommends #1 at 100 amps and #3 at 80 amps. So, #2 should be fine up to 90 amps or so. There are many calculators like this to be found on the interwebs and the 3% voltage drop recommended by the National Electrical Code is just that, a recommendation. It is not found anywhere in the text of the Code and is therefore unenforceable. However, if you want your equipment to work properly then it is good advice to heed.
I seriously doubt you will ever have more than 80 amps on the circuit unless you are an indoor farmer or cryptocurrency miner. In that case you should go larger on the wire and panel.