new Handle:hSpawns;

public OnPluginStart() {
    hSpawns = CreateArray();
}

public OnMapStart() {
    new iEntity = -1;

    ClearArray(hSpawns);

    while ( (iEntity = FindEntityByClassname(iEntity, "info_player_start") != -1 ) {
        PushArrayCell(hSpawns, iEntity);
    }
}

/* to teleport the player */

new Float:fOrigin[3];
new spawn = GetRandomInt(0, GetArraySize(hSpawns)-1);
GetEntPropVector(iEntity, Prop_Send, "m_vecOrigin", fOrigin);
TeleportEntity(client, fOrigin, NULL_VECTOR, NULL_VECTOR);