Hi everyone, For a month or two I’ve felt like my car doesn’t have quite as much “oomf” to it anymore, however it is only a 1.2 engine and I’m a relatively new driver so a lot of people reassured me that it was just because I’d gotten used to driving so my accelerating was smoother.

Today on a journey I had to use my hazards for the first time - I felt as though my car was struggling to speed up, and that when I took my foot off the accelerator the speed would drop quite quickly. It was manageable until at one point my car just stuck at 61mph, I tried genuinely flooring it, and it just would not go any faster. At this point made the decision to come off the motorway and go the back roads instead. Shortly after, I’m driving at about 55mph and it just suddenly starts dropping. It went down to just over 30mph pretty quickly and just would not budge. I was accelerating (or trying to) but the car was actively slowing down. I put the hazards on, and eventually after about 15 minutes managed to get back up to speed by gearing down, overreving, gearing up and repeating - but with the way it was slowing down I really felt it was going to conk out completely.

Got to a point of the journey where motorway was pretty much unavoidable (thankfully was quiet and had a hard shoulder) and again it happened a few times where it just slowed down, stuck around 55-60 and would not speed up. Had to drop from 5th to 4th, get up to about 65 and then put back into 5th to be able to get back up to speed. The weird thing is that about 50% of the time this happened, after getting it back up to speed and in the right gear, shortly after the acceleration would temporarily be really sensitive and seem to shoot up to a higher speed quickly.

No high revs, weird sounds or smells, or any warning lights. Battery replaced about 4 months ago. It’s a 15 year old Corsa with about 93k miles on it. No advisories on last MOT (feb)

Im going to get it looked at, but just wondering what kind of issues I may be looking at so I have a ballpark figure for money to put aside, can hopefully avoid getting ripped off, and know how urgently it needs sorting.

Tl;DR Car acceleration inconsistent, losing power/slowing down randomly and having to over rev in lower gear to speed back up. Any ideas what could be causing it?