VW beetle. 98

Was driving at highway speed in Canada's north. Coming to top of hill and I realized I had lost acceleration of any kind. Pedal to the floor and I could barely achieve 100km/hour in fourth. The high wind was even causes deceleration. Fourty minutes later in Valleyview, AB, CA; I pulled into a Tim hortons and shut it off. Had a coffee and breakfast, filled tank with $33 and headed out and all seemed fine.
I added the file treatment stuff.
Can someone formulate a cause of the low power and lacking torque and inability to accelerate? Dirty fuel? Stuck cruise control? Went 1500 kms after that.. All is good but with concern!
Thanks bill

It called "limp mode". It causes the ECU to reduce power when it "sees" conditions such as overboost, etc that could be able to cause engine damage. It is reset to "normal" when you shut the engine off and restart, until the conditions reoccurr.
You will have to do some searching to find (all) the causes, but typically vacuum leak(s), stuck turbo vanes/actuator, etc.
Most common for the condition to occur when extended accelerations in higher gears or long uphill grades.
Most likely your intake is clogged up, the vacuum system has some leaks, the turbo variable vane mechanism is stuck, and/or all those.
It can wait until you get home to remedy it if you can suffer thru the trip with it as is.
Remember that a restart will return it to normal until conditions require a reoccurrence.