Having some trouble with my Toyota Avensis 2000 model

Hi!

So I have a Toyota Avensis 2000 model which needs a oil change and some other repairs to be done. I'm hoping to do the oil change myself and just get a shop to do the heavier repairs, but two issues have come up.

1. I can't find the damn oil filter. I'm used to it being at least visible from under the hood from my previous car. Anyone know where it is?

2. If I lets say park my car on a friday afternoon and use public transport on the weekend and don't use it before monday morning again, I get a strange problem with the car.

I'll start it up monday morning and head to work. But for some reason the car gets "stuck" on just below 2000 rpms. What I mean is that if I'm driving in the 3rd gear and try to accelerate up in order to shift to the 4th gear, it goes fine until I reach about 1800 - 1900 rpms. Then the car "stalls" and no matter how hard I press the gas pedal, it just won't give me more power and won't get past this point. Unless I change the gear. I'll shift to 4th and then accelerate fine up until the same point again in order to shift to the 5th gear. This happens for all the gears (maybe not the first, I can't remember right now).

This continues all the way (15 minute drive). But when I get back to the car after work and head home, theres no problem, none. And for the rest of the week it won't happen again, but at once I let the car stand still for a couple of days it happens again.

At first I thought it could be the brakes/handbrake considering I need to change my brake discs (+ pads) in the front as well as adjust the handbrake wire, which I'm going to get done next week. But that doesn't really make sense to me, considering that it only happens when I let it stand still for a couple of days.

I've been grinding my head about this one the last couple of days and was hoping someone could help me out, it would be really appreciated. :)