1998 ford galaxy 1.9 TDI ?

hello,could someone help me with my 1998 ford galaxy 1.9TDI. glow plug light would not come on when i went to try and start car, so it didn't start so i found where the relay was and just touched number 109 relay and tried the car and glow plug light briefly flashed and the car started, so i have been running the car for about a week and all of a sudden whilst driving the car stopped, so back to the relay touched relay and got glow plug light again so started went out in it, but whilst driving it felt like it was going to stop again. so could you help please cos i cant keep going to relay all the time because its really hard to get to...... THANKS