Welcome Struths,
depending on the aircraft you sat in, this could be perfectly normal: Torque and propwash, see here:
Understanding Propeller Torque and P-Factor.
Then, again depending on the aircraft, play around with trimming: elevator trim, rudder trim, and aileron trim. Not every plane has all, the spits e.g. only have elevator and rudder trim.
No aircraft will ever fly straight (with no control input) at every combination of altitude, propeller pitch, and manifold pressure.
Artist