L322 2002 4.4 cutting out

Hi, I have a problem with my 02 4.4 HSE, I’m driving along and suddenly slow down to turn a corner and then the car just cuts out, as if it had stalled, it’s only ever happened to me twice, one across from 2 days, but today, it had cut out on my husband twice in one day. We just pull over, switch car off and start it back up again and off we go. What could the problem be? I don’t have problems changing gears, but hubby thinks it takes its time changing up a gear, it also rough idles sometimes on first start up, I bought 1 ignition coil, how do I find out which one to change? As I believe there’s 8 of them. I plan to buy 7 more, as if I bought 8 in one go, it would have cost me over £200.
Plus anyone have a tutorial, video or instructions on how to change an ignition coil? TIA.

First step before wasting cash is to get it on diagnostics. Why would you suspect ignition coils with no evidence?