I have a 2002 ford focus. This morning it made a clicking sound and would not start. About 20 minutes later it started, I turned it back off and it started again. What could the problem be??? I am afraid it will do this again.

The clicking sound is the starter motor trying to engage, but does not engage because of low electrical current. Knowing that you started your motor with jump leads this morning indicates that your car's battery needs charging/replacement.
Hope this helps.

Instrument cluster maybe !

timing belt gone

may be a bad alt check voltage while running should be about 14 volts

clean all batter connections including any samll wires on battery.

moisture in your distributor cap.

dry out the distributor cap..

They are two most common problems with this vehicle that will cause it to do this 1 bad distributor and the other bad MAIN relay. I need you to check for spark and gas when this vehicle does not start, contact if you need help checking when you figured out whats missing when you fail to start I will give you the answer, Good luck and thanks for using FIX YA

Charge Battery.
Put key in driver door. turn fully clockwise for 3 sec. Turn fully CCW for 3 sec. Get in car, put key in ignition and try again.

PossibleTemp Sensor as it Determines for ECM to go full Rich in cold weather If That Doesnt Correct it. I Would Just Get a Block Heater then it wont Sence COLD temp and go Full RICH.

you can use the ford fault codes to check with out going to a dealer this may reset the poss ecu fault
easy check system without a laptop ?? as long as you have a digital trip
before you start your car press and hold the trip reset button turn the key to start your car and keep the button pressed within 10 seconds the clock will show 0000 when this appears each time you press the trip button it will self test differant systems full dash clock sweep all warning lights engine rpm alternator charge engine core temp fuel flow and will list fault codes which can be checked on this site atleast it will save you afew quid/euros dollers on ford checking it for you and you will know what if anything needs doing i hope this helps