@nikhilvayedaa
Check every trainer you have installed for a 'vehicles never get dirty' etc option & make sure it's not enabled.
Confirm whether it happens if you rename your 'scripts' folder (if exist within main GTA V folder. If no 'scripts' folder ignore this) to something else temporarily & test load the game.
Confirm whether it happens if you rename your 'mods' folder to something else temporarily & test load the game.
It's likely one of them will highlight something. Let me know what you discover