A couple of questions that will help me fix your problem(might):
1. Have you installed any mods recently?
2. Have you removed any mods recently?(If yes, state the program and the file/name of the mod.
3. When was the last time you were able to play?
4. Where does your game freeze?(Upon starting, once entering a car, shooting a player, etc..)
Some tips to fix:
1. Remove & Uninstall SA-MP and reinstall it.
2. Remove & Delete any .asi and CLEO modification.
3. Delete gta_sa(or gta-sa).set in your GTA San Andreas User Files
This could be due to your game missing some .dff/.txd files, which can be solved by downloading an unmodded GTA3.img.