Is your toilet is gurgling or sucking air? Slow to drain?
If we get there before the situation is dire we are usually able to show you the problem before and after we clear the line, which will help you understand the problem and the possible work required.
common causes are tree roots entering sewer pipes through cracked, broken or misaligned pipes, once the tree roots find the water they grow and grow until they completely block the pipe.
If this sounds like your problem let your plumber know before the sewer is blocked completely it will save them time and you money.