What can I don if my experience is not relevant for the position I am applying for?
Think about the abilities and capacities that you can transfer and would be applicable to the new job. Remember what you have acquired in your previous work or other activities and/or experiences in your life: to work under pressure, in a team, using languages in your work or when you travel, communication skills, knowing how to carry out or compile reports, to convince people (in social situations, your friends, to negotiate the rent for a house...)
How to explain the periods of work inactivity?
All along, have you been sitting on the sofa or have you done things? Think, it is possible that you dedicated yourself to update your knowledge or to study IT, languages, or you have decided to have children and dedicate your time to them, which demonstrates your capacity for organization, forecasting, taking into account details and "to work under pressure, without time to rest and in a very noisy atmosphere". Reflect and explain in your CV the abilities learned and how to solve problems.
I have a lot of work experience, but... I have never made a resume
After a long time working, looking for employment can be very difficult. IT is possible that you only filled out a form 15-20 ago years and since then you have worked in the same company or you have always been contacted and offered new jobs. At this moment you must raise the most important things, the achievements attained, and plan all the information that you consider interesting for the position you choose.
I have spent a while travelling. How I can reflect this in an interesting way in my resume?
Write about the situations that you have had to solve and the experiences that have had the biggest impact on you and conclude with what you have learned (always in relation to the position or functions that you are aiming for).
Does it adequately reflect the temporary work carried out while studying or were you looking for a job suited to your preparation and experience?
In a CV of two pages you are not going to make a list of all the temporary jobs you have had, but emphasise those in which you have been able to apply your knowledge and abilities or in which after a few days they gave you more responsibility, even though it was in a short time space.