Ford Fiesta (2010) accelerator not working once car started!

Mileage:99700km.  
Car has issues after it starts every once in a while. No consistency to it but lately it has been more frequent when I go to use it to go home after sitting dormant all day during a work shift. It starts up fine, you put it into 1st gear no bother, lift the clutch and go to move off. The car will move with the clutch but once you’ve released the it - you’re free falling. The accelerator doesn’t do anything for at least 2 minutes. The wipers also don’t work during this period and a battery symbol appears on the dash despite the car running fine!

We have tested the battery and there’s nothing loose around it / it’s showing up as being fine. Its not failing or anything of the sort.

And now to add onto it my lights are flickering on and off while driving. Either one at a time or both. Almost like the bulbs are dying but this can’t be the case as it is both practically simultaneously. They don’t do this while at a standstill.

The car also sometimes just cuts out and turns itself off while driving. (We don’t have start stop and no I’m not conking🤣) This has only ever happened at slow speeds (thank god) but nonetheless concerning. It got plugged in by the garage on numerous occasions with nothing showing up and it’s recently been serviced. 
Any help desperately appreciated…..